From 1a6d6e7d5939e32b8448d4512058cc834f1cefc6 Mon Sep 17 00:00:00 2001
From: vidhigupta20 <76245203+vidhigupta20@users.noreply.github.com>
Date: Sat, 8 Oct 2022 18:11:48 +0530
Subject: [PATCH] Create N-Queens.cpp

---
 backtracking/N-Queens.cpp | 44 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 backtracking/N-Queens.cpp

diff --git a/backtracking/N-Queens.cpp b/backtracking/N-Queens.cpp
new file mode 100644
index 0000000..5401af5
--- /dev/null
+++ b/backtracking/N-Queens.cpp
@@ -0,0 +1,44 @@
+bool isPossible(int row,int col,vector<string>& board,int n){
+		int duprow =row;
+		int dupcol=col;
+		while(row>=0 && col>=0){
+			if(board[row][col] == 'Q') return false;
+			col--;
+			row--;
+		}
+		row = duprow;
+		col = dupcol;
+		while(col>=0){
+			if(board[row][col] == 'Q') return false;
+			col--;
+		}
+		col = dupcol;
+		while(row<n && col>=0){
+			if(board[row][col] == 'Q') return false;
+			col--;
+			row++;
+		}
+		return true;
+	}
+	void solve(int col,vector<vector<string>> &ans,vector<string> &board,int n){
+		if(col==n){
+			ans.push_back(board);
+			return;
+		}
+		for(int row=0;row<n;row++){
+			if (isPossible(row,col,board,n)){
+				board[row][col] = 'Q';
+				solve(col+1,ans,board,n);
+				board[row][col]='.';
+			}
+		}
+	}
+	vector<vector<string>> solveNQueens(int n) {
+		vector<vector<string>> ans;
+		vector<string> board(n);
+		string s(n,'.');
+		for(int i=0;i<n;i++) 
+			board[i] = s;
+		solve(0,ans,board,n);
+		return ans;
+	}