739. Daily Temperatures**

​​https://leetcode.com/problems/daily-temperatures/​​

题目描述

Given a list of daily temperatures ​​T​​​, return a list such 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, put ​​0​​ instead.

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

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

C++ 实现 1

其实这道题就是求 Next Great Number, 比如该思路还可以处理 ​​496. Next Greater Element I*​​​ 以及 ​​1019. Next Greater Node In Linked List**​​. 维护一个单调栈, 从栈顶到栈底元素是递增的(实际上栈中保存的是元素的索引值).

class Solution {
public:
    vector<int> dailyTemperatures(vector<int>& T) {
        vector<int> res(T.size(), 0);
        stack<int> st;
        for (int i = 0; i < T.size(); ++ i) {
            while (!st.empty() && T[i] > T[st.top()]) {
                auto idx = st.top();
                st.pop();
                res[idx] = i - idx;
            }
            st.push(i);
        }
        return res;
    }
};