503.下一个更大元素II

class Solution {
public:
    vector<int> nextGreaterElements(vector<int>& v) {
        vector<int>res(v.size(),-1);
        vector<int>s;
        int n = v.size();
        for(int i=0;i<n*2;i++){
            while(!s.empty()&&v[s.back()]<v[i%n]){
                int idx = s.back();
                s.pop_back();
                res[idx]=v[i%n];
            }
            s.push_back(i%n);
        }
        return res;
    }
};