739. Daily Temperatures**

739. Daily Temperatures**

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

題目描述

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++ 實現 1

其實這道題就是求 Next Great Number, 比如該思路還可以處理 496. Next Greater Element I* 以及 1019. Next Greater Node In Linked List**. 維護一個單調棧, 從棧頂到棧底元素是遞增的(實際上棧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;
    }
};