739 Daily Temperatures

739. Daily Temperatures

1. Question

Given a list of dailytemperatures, produce a list that, for each day in the input, tells you how many days you would have to wait until a warmer temperature. If there is no future day for which this is possible, put0instead.

For example, given the listtemperatures = [73, 74, 75, 71, 69, 72, 76, 73], your output should be[1, 1, 4, 2, 1, 1, 0, 0].

Note:The length oftemperatureswill be in the range[1, 30000]. Each temperature will be an integer in the range[30, 100].

2. Implementation

(1) Monotone Stack

class Solution {
    public int[] dailyTemperatures(int[] temperatures) {
        int n = temperatures.length;
        int[] res = new int[n];
        Stack<Integer> stack = new Stack<>();

        for (int i = 0; i < n; i++) {
            int curTemp = temperatures[i];

            while (!stack.isEmpty() && curTemp > temperatures[stack.peek()]) {
                res[stack.peek()] = i - stack.peek();
                stack.pop();
            }
            stack.push(i);
        }
        return res;
    }
}

3. Time & Space Complexity

Monotone Stack: 时间复杂度O(n), 空间复杂度O(n)