【代码随想录Day58 单调栈 part01】739.每日温度、496.下一个更大元素Ⅰ

Day58

739.每日温度

class Solution {
    public int[] dailyTemperatures(int[] temperatures) {
        Stack<Integer> stack = new Stack<>();
        int res[] = new int[temperatures.length];
        stack.push(0);
        for (int i = 1; i < temperatures.length; i++) {
            if (temperatures[i] <= temperatures[stack.peek()]) {
                stack.push(i);
            } else {
                while (!stack.isEmpty() && temperatures[i] > temperatures[stack.peek()]) {
                    int tmp = stack.pop();
                    res[tmp] = i - tmp;
                }
                stack.push(i);
            }
        }
        return res;
    }
}

496.下一个更大元素Ⅰ

class Solution {
    public int[] nextGreaterElement(int[] nums1, int[] nums2) {
        int n = nums1.length;
        int m = nums2.length;
        int res[] = new int[m];
        int ans[] = new int[n];
        Arrays.fill(res, -1);
        Map<Integer, Integer> map = new HashMap<>();
        Stack<Integer> stack = new Stack<>();
        stack.push(0);
        map.put(nums2[0], 0);
        for (int i = 1; i < m; i++) {
            map.put(nums2[i], i);
            if (nums2[i] <= nums2[stack.peek()]) {
                stack.push(i);
            } else {
                while (!stack.isEmpty() && nums2[i] > nums2[stack.peek()]) {
                    int tmp = stack.pop();
                    res[tmp] = nums2[i];
                }
                stack.push(i);
            }
        }
        for (int i = 0; i < n; i++) {
            ans[i] = res[map.get(nums1[i])];
        }
        return ans;
    }
}