PQ #4 - N Queens Problem using Backtracking | Easiest Solution REVEALED !!

The N Queen is the problem of placing N chess queens on an N×N chessboard so that no two queens attack each other. For example, the following is a solution for 4 Queen problem.
{ -, Q, -, -}
{ -, -, -, Q}
{ Q, -, -, -}
{ -, -, Q, -}

In this video, we will not only understand the way of solving the N Queen Problem, but also we will know, what is backtracking, and how we should solve any problem on backtracking. Then with the help of the proper visual display board, we will solve and explain the n queen problem solution using the backtracking algorithm. And once we are done, then we will start with the implementation of the n-queen backtracking algorithm with the help of java code. So lets get started:

► [IMPORTANT]

This question was asked in Amazon, Flipkart, Microsoft, Apple.

► **This video comes under "Hard" section of interview questions.
Q1: Snake and ladder problem:
Q2: Meeting Room Problem || Train Platform Problem:
Q3: Median of Stream of Running Integers:
Q4: N Queens Problem using Backtracking :

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[mohamedazizjnayah]

thank you Very good explanation😊, we need more videos

[dragonhot]

ohh wow straight abd understandable and clear code no mess

[bhagyaagasar]

can you provide of N-queen problem video ppt..please if possible

[akashchhabria]

Solution for the leetcode problem:(I removed the row check loop) class Solution {

public boolean isSafe(char[][] chessBoard, int row, int column, int n) {


for(int i = 0; i < row; i++){
if(chessBoard[i][column] == 'Q') return false;
}

for(int i = row - 1, j = column - 1 ; i >=0 && j>=0;i--, j--){
if(chessBoard[i][j] == 'Q') return false;
}

for(int i = row - 1, j = column + 1 ; i >=0 && j < n;i--, j++){
if(chessBoard[i][j] == 'Q') return false;
}

return true;



}

public List<String> constructBoard(char[][] chessBoard, int n){
List<String> Board = new ArrayList<>();
for(int i = 0; i < n; i++){
Board.add(new String(chessBoard[i]));
}
return Board;
}
public List<List<String>> solveNQueens(int n) {
List<List<String>> result = new ArrayList<>();
char[][] chessBoard = new char[n][n];
for(int i = 0; i < n; i++){
Arrays.fill(chessBoard[i], '.');
}
solve(0, chessBoard, result, n);


return result;


}

public void solve(int row, char[][] chessBoard, List<List<String>> result, int n ){

if (row == n) {
result.add(constructBoard(chessBoard, n));
return;
}


for(int column = 0; column < n; column++){
if(isSafe(chessBoard, row, column, n)){
chessBoard[row][column] = 'Q';
solve(row + 1, chessBoard, result, n);
chessBoard[row][column] = '.';
}
}
}
}

[yarramneninikhil]

Bro how to master dsa please provide me roadmap and resources

[madhuribende]

Tell explanation that how they can't get attacked