NQueens.cpp

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
#define ff                 first
#define ss                 second
#define endl               "\n"
#define ll                 long long
#define ld                 long double
#define loop(a, b, c)      for(ll (a) = (b); (a)<=(c); (a)++)
#define looprev(a, b, c)   for(ll (a) = (b); (a)>=(c); (a)--)
#define pb                 push_back
#define mp                 make_pair
#define pii                pair<ll, ll>
#define vi                 vector<ll>
#define mii                map<ll, ll>
#define ump                unordered_map<ll, ll>
#define pqb                priority_queue<ll>
#define pqs                priority_queue<int, vi, greater<ll> >
#define setbits(x)         __builtin_popcountll(x)
#define zrobits(x)         __builtin_ctzll(x)
#define mod                1000000007
#define inf                1e18
#define ps(x, y)           fixed<<setprecision(y)<<x
#define mk(arr,n,type)     type *arr = new type[n];
#define w(t)               int x; cin>>x; while(x--)
// mt19937                    rng(chrono::steady_clock::now,time_since_epoch(),count());
typedef tree<pair<int, int>, null_type, less<pair<int, int>>, rb_tree_tag, tree_order_statistics_node_update> pbds;

    
void file_i_o(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	/* #ifndef ONLINE_JUDGE
		freopen("input.txt", "r", stdin);
		freopen("output.txt", "w", stdout);
	#endif */
}





bool notPresentCol(int col, int row, vector<int>& board, int n) {

	for(int i = 0; i < row; i++) {
		int idx = i * n + col;
		if(board[idx] == 1)
			return false;
	}

	return true;

}



bool notPresentDiag(int col, int row, vector<int>& board, int n) {

	int i = row - 1;
	int j = col - 1;

	while(i >= 0 and j >= 0) {
	int idx = i * n + j;
		if(board[idx] == 1)
			return false;
		
		i -= 1;
		j -= 1;
	}

	i = row - 1;
	j = col + 1;


	while(i >= 0 and j < n) {
		int idx = i * n + j;
		if(board[idx] == 1)
			return false;
	
		i -= 1;
		j += 1;
	}

	return true;


}




void rec(int row, int n, vector<int>& board, vector<vector<int>>& config) {
	
	if(row == n) {
		config.push_back(board);
		return;
	} 

	for(int col = 0; col < n; ++col) {
		if(notPresentCol(col, row, board, n) and notPresentDiag(col, row, board, n)) {
			int idx = row*n + col;
			board[idx] = 1;
			rec(row+1, n, board, config);
			board[idx] = 0;
		}
	}

}



vector<vector<int>> solveNQueens(int n) {
    // Write your code here.
	
	vector<int> board(n*n, 0);

	vector<vector<int>> config;

	rec(0, n, board, config);

	return config;   
    
}








int main(int argc, char const *argv[]) {

	file_i_o();

	clock_t start, end;
    start = clock();

	w(t){

	/*  Write Code Here  */

	}

	end = clock();
	
	double time_taken=double(end-start)/double(CLOCKS_PER_SEC);
    cerr<<"\nTime : "<<fixed<<time_taken<<setprecision(5)<<" s \n";
    cerr<<"\n"<< "Coded By : S!r Black-D3vil" <<"\n";

	return 0;
}