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weekly contest 339
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‎README.md

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@@ -6,6 +6,7 @@ leetcode url: <https://leetcode.cn/u/cctest/>
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* ☀️ [weekly contest 339](src/main/java/weekly/wk339.java) 模拟 | 哈希 | 贪心 | 平衡树
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* ☀️ [weekly contest 338](src/main/java/weekly/wk338.java) 贪心 | 谈心 | 前缀和+二分 | 拓扑排序
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* ☀️ [weekly contest 337](src/main/java/weekly/wk337.java) 模拟 | 模拟 | 回溯 | 同余分组
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* 🐎️ [weekly contest 336](src/main/java/weekly/wk336.java) 模拟 | 排序 | 异或前缀和 | 贪心
@@ -53,6 +54,7 @@ leetcode url: <https://leetcode.cn/u/cctest/>
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* 🐶 [weekly contest 290](src/main/java/weekly/wk290.java)
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* 🐭 [weekly contest 280](src/main/java/weekly/wk289.java)
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* 🐸 [biweekly contest 101](src/main/java/weekly/wkb101.java) 哈希 | 滑动窗口 | 并查集 | BFS
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* 🐸 [biweekly contest 100](src/main/java/weekly/wkb100.java) 四维 | 贪心 | 堆 | 二分
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* 🐸 [biweekly contest 99](src/main/java/weekly/wkb99.java) 贪心 | 递推 | 区间合并 | 换根DP
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* 🐸 [biweekly contest 98](src/main/java/weekly/wkb98.java)

‎src/main/java/weekly/wk339.java

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package weekly;
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import java.util.ArrayDeque;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.Comparator;
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import java.util.HashSet;
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import java.util.LinkedList;
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import java.util.List;
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import java.util.PriorityQueue;
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import java.util.Queue;
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import java.util.Set;
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import java.util.TreeSet;
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public class wk339 {
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//模拟
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static public int findTheLongestBalancedSubstring(String s) {
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int i = 0;
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int ans = 0;
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while (i < s.length()) {
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int zero = 0;
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while (i < s.length() && s.charAt(i) == '0') {
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zero++;
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i++;
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}
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int one = 0;
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while (i < s.length() && s.charAt(i) == '1') {
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one++;
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i++;
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}
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ans = Math.max(Math.min(zero, one) * 2, ans);
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}
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return ans;
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}
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//hash
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public List<List<Integer>> findMatrix(int[] nums) {
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Arrays.sort(nums);
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int pre = nums[0];
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int count = 1;
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List<List<Integer>> res = new ArrayList<>();
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for (int i = 1; i < nums.length; i++) {
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if (nums[i] == pre) {
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count++;
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} else {
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while (res.size() < count) {
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res.add(new ArrayList<>());
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}
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for (int j = 0; j < count; j++) {
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res.get(j).add(pre);
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}
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pre = nums[i];
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count = 1;
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}
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}
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while (res.size() < count) {
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res.add(new ArrayList<>());
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}
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for (int j = 0; j < count; j++) {
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res.get(j).add(pre);
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}
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return res;
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}
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//贪心
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static public int miceAndCheese(int[] reward1, int[] reward2, int k) {
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PriorityQueue<Integer> priorityQueue = new PriorityQueue<>(Comparator.reverseOrder());
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int sum = 0;
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for (int i = 0; i < reward1.length; i++) {
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int dis = reward1[i] - reward2[i];
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priorityQueue.add(dis);
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sum += reward2[i];
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}
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while (k > 0) {
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sum += priorityQueue.poll();
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k--;
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}
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return sum;
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}
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//直接遍历超时
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/*static public int[] minReverseOperations(int n, int p, int[] banned, int k) {
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int[] res = new int[n];
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Set<Integer> banSet = new HashSet<>();
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for (int i : banned) {
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banSet.add(i);
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}
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//存储未查询的点
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Set<Integer> treeSet=new TreeSet<>();
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for (int i = 0; i < n; i++) {
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treeSet.add(i);
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}
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Queue<Integer> queue = new LinkedList<>();
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queue.add(p);
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treeSet.remove(p);
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for (int i = 0; i < res.length; i++) {
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res[i] = -1;
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}
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res[p] = 0;
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boolean[] visited = new boolean[n];
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int step = 0;
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while (!queue.isEmpty()) {
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step++;
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int size = queue.size();
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while (size-- > 0) {
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int cur = queue.poll();
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visited[cur] = true;
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int r=cur+k-1;
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int l=cur-k+1;
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for (int i = k; i > 1; i -= 2) {
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//左移
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int left = cur - i + 1;
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int ll = (l++);
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int lr = ll+k-1;
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//右移动
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int right = cur + i - 1;
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int rr=(r--);
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int rl=rr-k+1;
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if (left >= 0 && lr<n&&ll>=0 && !visited[left] && !banSet.contains(left)) {
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visited[left] = true;
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queue.add(left);
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res[left] = step;
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}
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if (right < n &&rl>=0&&rr<n && !visited[right] && !banSet.contains(right)) {
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visited[right] = true;
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queue.add(right);
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res[right] = step;
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}
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}
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}
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}
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return res;
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}*/
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//广度优先+有序集合
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static public int[] minReverseOperations(int n, int p, int[] banned, int k) {
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int[] res = new int[n];
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Set<Integer> banSet = new HashSet<>();
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for (int i : banned) {
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banSet.add(i);
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}
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banSet.add(p);
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//存储未查询的点
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TreeSet<Integer> treeEven = new TreeSet<>();
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TreeSet<Integer> treeOdd = new TreeSet<>();
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TreeSet<Integer> sets[] = new TreeSet[2];
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sets[0] = treeEven;
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sets[1] = treeOdd;
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treeEven.add(n);
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treeOdd.add(n);
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for (int i = 0; i < n; i++) {
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if (banSet.contains(i)) continue;
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if (i % 2 == 0) {
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treeEven.add(i);
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} else {
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treeOdd.add(i);
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}
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}
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Queue<Integer> queue = new LinkedList<>();
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queue.add(p);
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for (int i = 0; i < res.length; i++) {
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res[i] = -1;
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}
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int step = 0;
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while (!queue.isEmpty()) {
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int size = queue.size();
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while (size-- > 0) {
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Integer i = queue.poll();
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res[i] = step;
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// 从 mn 到 mx 的所有位置都可以翻转到
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int mn = Math.max(i - k + 1, k - i - 1);
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int mx = Math.min(i + k - 1, n * 2 - k - i - 1);
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TreeSet<Integer> s = sets[mn % 2];
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for (int j = s.ceiling(mn); j <= mx; j = s.ceiling(mn)) {
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queue.add(j);
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s.remove(j);
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}
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}
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step++;
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}
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return res;
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}
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public static void main(String[] args) {
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minReverseOperations(4, 0, new int[]{1,2}, 4);
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}
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}

‎src/main/java/weekly/wkb101.java

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package weekly;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.Collections;
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import java.util.HashMap;
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import java.util.HashSet;
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import java.util.LinkedList;
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import java.util.List;
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import java.util.Map;
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import java.util.Queue;
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import java.util.Set;
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public class wkb101 {
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//哈希
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public int minNumber(int[] nums1, int[] nums2) {
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Arrays.sort(nums1);
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Arrays.sort(nums2);
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Set<Integer> set = new HashSet<>();
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for (int i : nums2) {
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set.add(i);
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}
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for (int i : nums1) {
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if (set.contains(i)) return i;
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}
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return Math.min(nums1[0] * 10 + nums2[0], nums2[0] * 10 + nums1[0]);
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}
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//滑动窗口
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public int maximumCostSubstring(String s, String chars, int[] vals) {
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int[] scores = new int[26];
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for (int i = 0; i < scores.length; i++) {
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scores[i] = i + 1;
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}
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for (int i = 0; i < chars.length(); i++) {
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char c = chars.charAt(i);
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scores[c - 'a'] = vals[i];
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}
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int max = 0;
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int sum = 0;
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for (int i = 0; i < s.length(); i++) {
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char c = s.charAt(i);
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sum += scores[c - 'a'];
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max = Math.max(sum, max);
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if (sum < 0) {
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sum = 0;
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}
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}
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return max;
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}
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//并查集
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class UnionFind {
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public final int[] parents;
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public int count;
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public UnionFind(int n) {
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this.parents = new int[n];
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reset();
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}
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public void reset() {
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for (int i = 0; i < parents.length; i++) {
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parents[i] = i;
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}
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count = parents.length - 1;
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}
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public int find(int i) {
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int parent = parents[i];
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if (parent == i) {
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return i;
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} else {
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int root = find(parent);
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parents[i] = root;
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return root;
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}
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}
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public boolean union(int i, int j) {
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int r1 = find(i);
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int r2 = find(j);
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if (r1 != r2) {
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count--;
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parents[r1] = r2;
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return true;
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} else {
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return false;
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}
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}
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/* void isolate(int x) {
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if (x != parents[x]) {
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parents[x] = x;
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count++;
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}
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}*/
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}
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//并查集分组计算
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public long makeSubKSumEqual(int[] arr, int k) {
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UnionFind uf = new UnionFind(arr.length);
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for (int i = 0; i < arr.length; i++) {
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uf.union(i, (i + k) % arr.length);
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}
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Map<Integer, List<Integer>> map = new HashMap<>();
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for (int i = 0; i < arr.length; i++) {
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int key = uf.find(i);
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if (!map.containsKey(key)) map.put(key, new ArrayList<>());
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map.get(key).add(arr[i]);
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}
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long ans = 0;
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for (List<Integer> list : map.values()) {
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Collections.sort(list);
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int mid = list.get(list.size() / 2);
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for (Integer num : list) {
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ans += Math.abs(num - mid);
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}
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}
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return ans;
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}
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//bfs、迪杰斯特拉
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public int findShortestCycle(int n, int[][] edges) {
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Map<Integer, List<Integer>> map = new HashMap<>();
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for (int[] edge : edges) {
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if (!map.containsKey(edge[0])) map.put(edge[0], new ArrayList<>());
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if (!map.containsKey(edge[1])) map.put(edge[1], new ArrayList<>());
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map.get(edge[0]).add(edge[1]);
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map.get(edge[1]).add(edge[0]);
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}
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boolean[] visited = new boolean[n];
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for (int i = 0; i < n; i++) {
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help(map, i,n);
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}
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return ans == Integer.MAX_VALUE ? -1 : ans;
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}
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int ans = Integer.MAX_VALUE;
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void help(Map<Integer, List<Integer>> map, int cur, int n) {
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int[] dis = new int[n];
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Arrays.fill(dis, -1);
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dis[cur] = 0;
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Queue<int[]> queue = new LinkedList<>();
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queue.add(new int[]{cur, -1});
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while (!queue.isEmpty()) {
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int[] poll = queue.poll();
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int x = poll[0];
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int pre = poll[1];
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for (Integer y : map.getOrDefault(x, new ArrayList<>())) {
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//未访问过该点
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if (dis[y] < 0) {
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dis[y] = dis[x] + 1;
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queue.add(new int[]{y, x});
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//非第一次访问
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} else if(y!=pre) {
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ans = Math.min(ans, dis[x] + dis[y] + 1);
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}
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}
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}
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}
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}

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