does array represent heap

/*
Given an array A of size N, the task is to check if the given array represents a Binary Max Heap.

Input:
The first line of input contains an integer T denoting the number of test cases. Then T test cases follow. Each test case contains two lines. 
The first line of input contains an integer N denoting the size of the array. Then in the next line are N space separated array elements.

Output:
If array represents a Binary Max Heap, print "1", else print "0" (without quotes).

Constraints:
1 <= T <= 100
1 <= N <= 107
1 <= Ai <= 1015

Example:
Input:
2
6
90 15 10 7 12 2
6
9 15 10 7 12 11

Output:
1
0

Explanation:
Testcase 1: Array of first elements represents Binary Max Heap, so output is 1.
*/

#include <bits/stdc++.h>
#define ll long long int
using namespace std;

bool heapify(ll a[], ll n, ll i){
    ll root=i;
    ll left=2*i + 1;
    ll right=2*i + 2;
    if(left<n && a[left]>a[root]) return false;
    if(right<n && a[right]>a[root]) return false;
return true;
}

int main() {
	int t; cin>>t; while(t--){
	    ll n,flag=0; cin>>n; 
	    ll a[n]; for(ll i=0; i<n; i++) cin>>a[i];
	    for(ll i=n/2 -1; i>=0; i--){
	        if(heapify(a,n,i)==false){// for(i=0; i<n; i++){ if(a[(i-1)/2]>
	        //a[i]) 
	            flag=1;
	            break;
	        }
	    }
	    if(flag==1) cout<<0<<'\n';
	    else cout<<1<<'\n';
	}
	return 0;
}