303.cpp

// { Driver Code Starts
#include<bits/stdc++.h>
using namespace std;


 // } Driver Code Ends
class Solution
{
    public:
    //Function to find the next greater element for each element of the array.
    vector<long long> nextLargerElement(vector<long long> arr, int n){
         stack<int> s;
        vector<long long> ans(n,-1);
        s.push(arr[n-1]);
        
        for(int i=n-2;i>=0;i--){
            if(arr[i]<=s.top()){
                ans[i]=s.top();
                s.push(arr[i]);
            }
            else if(arr[i]>s.top()){
                while(!(s.empty()) && arr[i]>s.top()){
                    s.pop();
                }
                if(s.empty()){
                    s.push(arr[i]);
                    continue;
                }
                else{
                    ans[i]=s.top();
                    s.push(arr[i]);
                }
            }
        }
        return ans;
    }
};

// { Driver Code Starts.

int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        
        int n;
        cin>>n;
        vector<long long> arr(n);
        for(int i=0;i<n;i++)
            cin>>arr[i];
        
        Solution obj;
        vector <long long> res = obj.nextLargerElement(arr, n);
        for (long long i : res) cout << i << " ";
        cout<<endl;
    }
	return 0;
}  // } Driver Code Ends