代码随想录算法训练营|五十七天

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
            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;
    }
}