Coding/nextGreaterElement.cpp at main · ayushman-777/Coding · GitHub

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// { 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<long long> s;
        vector<long long> res(n);
        for(int i = n - 1; i>=0; i--) {
            if(!s.empty()) {
                while (!s.empty() && s.top() <= arr[i]) s.pop();
            }
            res[i] = s.empty() ? -1 : s.top();
            s.push(arr[i]);
        }
        return res;
    }
};

// { 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