nge1_496.cpp

classSolution {
public:
 vector<int> nextGreaterElement(vector<int>& nums1, vector<int>& nums2) {
int n = nums1.size(), m = nums2.size();
 vector<int> res(n, -1);
 stack<int> st;
 unordered_map<int, int> mp;
for(int i = 0; i < m; i++){
int val = nums2[i];
while(!st.empty() and val > st.top()){
 mp[st.top()] = val;
 st.pop();
 }
 st.push(val);
 }
for(int i = 0; i < n; i++){
int val = nums1[i];
if(mp.find(val) != mp.end()){
int nge = mp[val];
 res[i] = nge;
 }
 }
return res;
 }
};