class Solution {
public:
    vector<int> dailyTemperatures(vector<int>& temperatures) {
        int n = temperatures.size();
        vector<int>ans(n);
        stack<int>s;
        for(int i = 0; i < n; i++){
            while(s.size() && temperatures[i]>temperatures[s.top()]){
             int pre = s.top()   ;
             ans[pre] = i-pre;
             s.pop();
            }
            s.push(i);
        }
        return ans;
    }
};