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ZLBerZLBer
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weekly contest 322
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‎README.md

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@@ -5,6 +5,7 @@ Record leetcode contest and ideas every week, and encourage yourself to think mo
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leetcode url: <https://leetcode.cn/u/cctest/>
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* 🐎️ [weekly contest 322](src/main/java/weekly/wk322.java) 遍历 | 排序 | BFS | 二分图+BFS
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* ☀️ [weekly contest 320](src/main/java/weekly/wk320.java) 模拟 | DFS | 贪心 | DP
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* ☀️ [weekly contest 319](src/main/java/weekly/wk319.java) 模拟 | 暴力 | 置换环 | DP
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* ☀️ [weekly contest 318](src/main/java/weekly/wk318.java) 模拟 | 滑动窗口 | 双指针 | DP
@@ -53,7 +54,7 @@ leetcode url: <https://leetcode.cn/u/cctest/>
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* 🐸 [biweekly contest 78](src/main/java/weekly/wkb78.java)
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* 🐯 [biweekly contest 77](src/main/java/weekly/wkb77.java)
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🐽 🐮 🐗 🐵 🐒 🐴 🐎 🐫
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🐽 🐮 🐗 🐵 🐒 🐴 🐫
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‎src/main/java/weekly/wk322.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.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 wk322 {
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//ranking: 349 / 5085
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//直接判断
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public boolean isCircularSentence(String sentence) {
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String[] s = sentence.split(" ");
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for (int i = 0; i < s.length - 1; i++) {
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if (s[i].charAt(s[i].length() - 1) != s[i + 1].charAt(0)) {
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return false;
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}
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}
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//判断最后一个
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if (s[0].charAt(0) != s[s.length - 1].charAt(s[s.length - 1].length() - 1)) {
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return false;
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}
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return true;
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}
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//排序+双指针
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public long dividePlayers(int[] skill) {
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Arrays.sort(skill);
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long cur = -1;
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long ans = 0;
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for (int i = 0; i < skill.length / 2; i++) {
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long sum = skill[i] + skill[skill.length - i - 1];
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if (cur != -1 && sum != cur) {
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return -1;
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}
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cur = sum;
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ans += (long) skill[i] * skill[skill.length - i - 1];
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}
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return ans;
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}
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//求联通块的最小路径
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public int minScore(int n, int[][] roads) {
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boolean[] visit = new boolean[n + 1];
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int min = Integer.MAX_VALUE;
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Map<Integer, List<int[]>> map = new HashMap<>();
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for (int[] road : roads) {
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if (!map.containsKey(road[0])) {
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map.put(road[0], new ArrayList<>());
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}
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if (!map.containsKey(road[1])) {
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map.put(road[1], new ArrayList<>());
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}
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map.get(road[0]).add(new int[]{road[1], road[2]});
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map.get(road[1]).add(new int[]{road[0], road[2]});
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}
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Queue<Integer> queue = new LinkedList<>();
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queue.add(1);
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while (!queue.isEmpty()) {
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Integer cur = queue.poll();
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visit[cur] = true;
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for (int[] next : map.getOrDefault(cur, new ArrayList<>())) {
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if (visit[next[0]]) {
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continue;
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}
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min = Math.min(min, next[1]);
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queue.add(next[0]);
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}
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}
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return min;
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}
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//有些直觉的想法是错的，再做下去也不会对啦
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//只考虑到三个边的换不可以，其实所有奇数边都不行，所以要判断是不是二分图
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/*public int magnificentSets(int n, int[][] roads) {
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Map<Integer, Set<Integer>> map = new HashMap<>();
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UnionFind uf = new UnionFind(n + 1);
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for (int[] road : roads) {
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uf.union(road[0], road[1]);
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if (!map.containsKey(road[0])) {
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map.put(road[0], new HashSet<>());
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}
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if (!map.containsKey(road[1])) {
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map.put(road[1], new HashSet<>());
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}
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map.get(road[0]).add(road[1]);
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map.get(road[1]).add(road[0]);
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}
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if (!check(map)) {
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return -1;
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}
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Map<Integer, Integer> res = new HashMap<>();
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for (int i = 1; i < n; i++) {
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boolean[] visit = new boolean[n + 1];
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Queue<Integer> queue = new LinkedList<>();
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queue.add(i);
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int m = 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 cur = queue.poll();
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visit[cur] = true;
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for (Integer next : map.getOrDefault(cur, new HashSet<>())) {
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if (visit[next]) {
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continue;
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}
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queue.add(next);
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}
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}
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m++;
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}
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res.put(uf.find(i), Math.max(res.getOrDefault(uf.find(i), 0), m));
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}
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int ans = 0;
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for (Map.Entry<Integer, Integer> entry : res.entrySet()) {
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ans += entry.getValue();
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}
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return ans;
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}
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boolean check(Map<Integer, Set<Integer>> map) {
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for (Map.Entry<Integer, Set<Integer>> entry : map.entrySet()) {
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for (Integer two : entry.getValue()) {
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Set<Integer> three = map.getOrDefault(two, new HashSet<>());
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for (Integer integer : three) {
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if (entry.getValue().contains(integer)) {
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return false;
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}
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}
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}
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}
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return true;
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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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}*/
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//判断二分图
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//+ bfs求最长路径
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public int magnificentSets(int n, int[][] edges) {
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int[] visited = new int[n];
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Map<Integer, List<Integer>> map = new HashMap<>();
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for (int[] road : edges) {
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if (!map.containsKey(road[0] - 1)) {
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map.put(road[0] - 1, new ArrayList<>());
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}
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if (!map.containsKey(road[1] - 1)) {
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map.put(road[1] - 1, new ArrayList<>());
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}
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map.get(road[0] - 1).add(road[1] - 1);
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map.get(road[1] - 1).add(road[0] - 1);
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}
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timer = new int[n];
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int ans = 0;
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for (int i = 0; i < n; i++) {
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if (visited[i] != 0) continue;
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//该联通图的点数
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List<Integer> nodes = new ArrayList<>();
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if (!help(i, -1, nodes, map, 1, visited)) {
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return -1;
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}
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int max = 0;
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for (Integer node : nodes) {
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max = Math.max(max, bfs(node, map, n));
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}
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ans += max;
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}
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return ans;
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}
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int[] timer;
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int clock;
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int bfs(int index, Map<Integer, List<Integer>> map, int n) {
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Queue<Integer> queue = new LinkedList<>();
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queue.add(index);
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clock++;
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timer[index]=clock;
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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 poll = queue.poll();
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for (Integer next : map.getOrDefault(poll, new ArrayList<>())) {
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if (timer[next] == clock) continue;
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timer[next] = clock;
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queue.add(next);
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}
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}
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step++;
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}
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return step;
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}
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//染色标记法判断二分图
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boolean help(int node, int pre, List<Integer> nodes, Map<Integer, List<Integer>> map, int color, int[] visited) {
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if (visited[node] != 0) {
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return visited[node] == color;
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}
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visited[node] = color;
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nodes.add(node);
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for (Integer next : map.getOrDefault(node, new ArrayList<>())) {
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if (next == pre) continue;
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if (!help(next, node, nodes, map, -color, visited)) {
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return false;
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}
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}
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return true;
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}
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}

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