# Challenge: Place N Queens on an NxN Chessboard

In this lesson, you will be challenged with a classic recursion problem, placing N queens on an NxN chessboard.

## We'll cover the following

## Problem statement

You are given an NxN chessboard, and you are required to place N queens on this chessboard such that no queen is under threat from any other queen.

In chess a queen can move any number of steps horizontally, vertically, or diagonally.

This means that no queen should share a row, column, or diagonal with another queen.

### Input

As input, your function will take a number `n`

and a list of strings as `board`

.

```
n = 4
board = ["----",
"----",
"----",
"----"
]
```

### Output

Your function should return the updated list of strings, `board`

, such that no queen denoted by `q`

shares a row, column, or diagonal with another queen.

```
placeNQueens(n, board) =
["-q--",
"---q",
"q---",
"--q-"
]
```

## Coding challenge

You can use the `isSafe(i, j, board)`

function to test whether the position given by `i`

$^{th}$ row and `j`

$^{th}$ column is safe to place a queen. This function basically checks whether the box position given by row `i`

and column `j`

shares row, column, or diagonal with any other queen you had already placed on the `board`

.

Do not change the prototype of either function as these are being used for testing. You can make your own helper functions though.

This one is a little trickier, but at the same time, it unleashes the real power of recursion. Feel free to look at hints. Best of luck!

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