每日温度

739. 每日温度 - 力扣（LeetCode）

压入栈时的元素和栈内的元素比较，有三个情况，栈内元素大于等于压入栈时的元素，此时压入栈内；如果小于压入栈内的元素，先记录result，再在栈中弹出元素，一直循环，直到大于等于压入栈时的元素，才压入栈内。

public class Solution {public int[] DailyTemperatures(int[] temperatures) {int[] result = new int[temperatures.Length];Stack<int> stack = new Stack<int>();stack.Push(0);for(int i=1;i<temperatures.Length;i++){if(temperatures[i] < temperatures[stack.Peek()]){stack.Push(i);}else if(temperatures[i] == temperatures[stack.Peek()]){stack.Push(i);}else{while (stack.Count > 0 && temperatures[i] > temperatures[stack.Peek()]) {result[stack.Peek()] = i - stack.Peek();stack.Pop();}stack.Push(i);}}return result;}
}

下一个更大元素 I

496. 下一个更大元素 I - 力扣（LeetCode）

public class Solution {public int[] NextGreaterElement(int[] nums1, int[] nums2) {Stack<int> stack = new Stack<int>();Dictionary<int, int> map = new Dictionary<int, int>();int[] result = new int[nums1.Length];for (int i = 0; i < nums1.Length; i++) {map[nums1[i]] = i;}for (int i = 0; i < nums2.Length; i++) {while (stack.Count > 0 && nums2[i] > stack.Peek()) {int num = stack.Pop();if (map.ContainsKey(num)) {result[map[num]] = nums2[i];}}stack.Push(nums2[i]);}while (stack.Count > 0) {int num = stack.Pop();if (map.ContainsKey(num)) {result[map[num]] = -1;}}return result;}
}