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Merge branch 'neetcode-gh:main' into main
2 parents 02ebbb1 + b3d096b commit fc90108

11 files changed

+278
-20
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‎README.md

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‎csharp/0523-continuous-subarray-sum.cs

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public class Solution
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{
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public bool CheckSubarraySum(int[] nums, int k)
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{
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var remainder = new Dictionary<int, int>();
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remainder.Add(0, -1);
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var total = 0;
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for (var i = 0; i < nums.Length; i++)
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{
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total += nums[i];
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var r = total % k;
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if (!remainder.ContainsKey(r))
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remainder.Add(r, i);
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else if (i - remainder[r] > 1)
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return true;
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}
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return false;
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}
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}

‎java/0116-populating-next-right-pointers-in-each-node.java

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class Solution {
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public Node connect(Node root) {
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Node current = root;
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Node next = root == null ? null : root.left;
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while (current != null && next != null) {
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current.left.next = current.right;
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if (current.next != null) {
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current.right.next = current.next.left;
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}
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current = current.next;
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if (current == null) {
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current = next;
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next = current.left;
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}
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}
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return root;
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}
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}

‎java/0446-arithmetic-slices-ii-subsequence.java

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public class Solution {
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public int numberOfArithmeticSlices(int[] nums) {
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int res = 0;
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int n = nums.length;
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Map<Long, Integer>[] dp = new HashMap[n];
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for (int i = 0; i < n; i++) {
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dp[i] = new HashMap<>();
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}
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for (int i = 0; i < n; i++) {
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for (int j = 0; j < i; j++) {
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long diff = (long) nums[i] - (long) nums[j];
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dp[i].put(diff, dp[i].getOrDefault(diff, 0) + 1 + dp[j].getOrDefault(diff, 0));
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res += dp[j].getOrDefault(diff, 0);
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}
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}
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return res;
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}
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}

‎java/0938-range-sum-of-bst.java

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/*--------------------------
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Time Complexity: O(n)
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Space Complexity: O(n)
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---------------------------*/
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class Solution {
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public int rangeSumBST(TreeNode root, int low, int high) {
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if(root == null)
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return 0;
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if(root.val > high)
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return rangeSumBST(root.left, low, high);
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if(root.val < low)
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return rangeSumBST(root.right, low, high);
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return root.val + rangeSumBST(root.left, low, high) + rangeSumBST(root.right, low, high);
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}
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}

‎java/1209-remove-all-adjacent-duplicates-in-string-ii.java

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class Solution {
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public String removeDuplicates(String s, int k) {
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Stack<Pair<Character, Integer>> stack = new Stack<>();
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char[] ss = s.toCharArray();
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for (char current : ss) {
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if (!stack.isEmpty() && stack.peek().getKey() == current) {
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int topCharCount = stack.pop().getValue();
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stack.push(new Pair<>(current, topCharCount + 1));
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} else {
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stack.push(new Pair<>(current, 1));
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}
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if (stack.peek().getValue() == k) {
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stack.pop();
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}
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}
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StringBuilder result = new StringBuilder();
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while (!stack.isEmpty()) {
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Pair<Character, Integer> poppedPair = stack.pop();
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for (int i = 0; i < poppedPair.getValue(); i++) {
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result.append(poppedPair.getKey());
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}
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}
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return result.reverse().toString();
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}
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}

‎java/1235-maximum-profit-in-job-scheduling.java

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class Solution {
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int[][] intervals;
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Integer[] cache;
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public int jobScheduling(int[] startTime, int[] endTime, int[] profit) {
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int n = startTime.length;
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intervals = new int[n][3];
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cache = new Integer[n];
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for (int i = 0; i < n; i++) {
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intervals[i] = new int[]{startTime[i], endTime[i], profit[i]};
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}
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Arrays.sort(intervals, (a, b) -> Integer.compare(a[0], b[0]));
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return dfs(0);
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}
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private int dfs(int i) {
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if (i == intervals.length) {
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return 0;
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}
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if (cache[i] != null) {
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return cache[i];
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}
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// don't include
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int res = dfs(i + 1);
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// include
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int j = binarySearch(intervals, i, intervals[i][1]);
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cache[i] = res = Math.max(res, intervals[i][2] + dfs(j));
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return res;
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}
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private int binarySearch(int[][] intervals, int start, int target) {
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int left = start + 1;
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int right = intervals.length - 1;
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while (left <= right) {
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int mid = left + (right - left) / 2;
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if (intervals[mid][0] < target) {
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left = mid + 1;
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} else {
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right = mid - 1;
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}
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}
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return left;
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}
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}

‎kotlin/0155-min-stack.kt

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import kotlin.math.min
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class MinStack() {
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private class Node(var `val`: Int, var min: Int, var next: Node?)
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private var head: Node? = null
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fun push(x: Int) {
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if(head==null) head = Node(x,x,null) else head = Node(x, min(x,head?.min!!),head)
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private val stack = Stack<Int>()
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private val minStack = Stack<Int>()
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fun push(`val`: Int) {
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val currentMin = if (minStack.isNotEmpty()) minStack.peek() else Integer.MAX_VALUE
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val newMin = minOf(currentMin, `val`)
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stack.push(`val`)
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minStack.push(newMin)
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}
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fun pop() {
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head = head?.next
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if (stack.isNotEmpty()) {
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stack.pop()
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minStack.pop()
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}
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}
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fun top(): Int? {
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return head?.`val`
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fun top(): Int {
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return stack.peek()
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}
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fun getMin(): Int? {
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return head?.min
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fun getMin(): Int {
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return minStack.peek()
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}
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}

‎kotlin/0446-arithmetic-slices-ii-subsequence.kt

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// dp
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class Solution {
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fun numberOfArithmeticSlices(nums: IntArray): Int {
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var res = 0
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val dp = HashMap<Pair<Int, Long>, Int>()
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for (i in 0 until nums.size) {
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for (j in 0 until i) {
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val d = nums[i].toLong() - nums[j]
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dp[i to d] = (dp[i to d] ?: 0) + 1 + (dp[j to d] ?: 0)
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res += (dp[j to d] ?: 0)
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}
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}
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return res
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}
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}
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// recursion + memoization
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class Solution {
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fun numberOfArithmeticSlices(nums: IntArray): Int {
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val dp = HashMap<String, Int>()
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val count = HashMap<Long, MutableList<Int>>()
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nums.forEachIndexed { i, n ->
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count.getOrPut(n.toLong()) { mutableListOf() }.apply { add(i) }
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}
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fun dfs(i: Int, d: Long, s: Int): Int {
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dp["$i:$d:$s"]?.let { return it }
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var res = if (s > 2) 1 else 0
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count[nums[i] + d]?.forEach { j ->
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if (j > i) res += dfs(j, d, s + 1)
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}
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dp["$i:$d:$s"] = res
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return res
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}
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var res = 0
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for (i in 0 until nums.size) {
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for (j in i + 1 until nums.size)
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res += dfs(j, nums[j].toLong() - nums[i], 2)
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}
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return res
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}
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}

‎kotlin/0938-range-sum-of-bst.kt

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class Solution {
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fun rangeSumBST(root: TreeNode?, low: Int, high: Int): Int {
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root?: return 0
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return if (root.`val` > high) rangeSumBST(root.left, low, high)
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else if (root.`val` < low) rangeSumBST(root.right, low, high)
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else root.`val` +
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rangeSumBST(root.left, low, high) +
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rangeSumBST(root.right, low, high)
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}
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}

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