739. Daily Temperatures

• Difficulty: Medium

• Topics: Hash Table, Stack

• Similar Questions:

  • Next Greater Element I

Problem:

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].

Solutions:

class Solution {
public:
    vector<int> dailyTemperatures(vector<int>& T) {
        int n = T.size();
        vector<int> ret(n, 0);
        stack<int> stk;

        for (int i = 0; i < T.size(); ++i) {
            while (!stk.empty() && T[stk.top()] < T[i]) {
                ret[stk.top()] = i - stk.top();
                stk.pop();
            }

            stk.push(i);
        }

        return ret;
    }
};