sape/queens.html

<script>
// Based on: https://stackoverflow.com/questions/75486408/n-queens-problem-using-backtracking-in-javascript
   function nQueen(boolArrBoard,row){
       if(row === boolArrBoard.length){
           display(boolArrBoard)
           return 1 //count*
       }
   
       let count = 0
       //placing the queen and checking every row and column*
       for(let col_ = 0; col_ < boolArrBoard.length; col_++){
			let col = indexes[col_];
           //place the queen if it is safe *
           if(isSafe(boolArrBoard,row,col)){
               boolArrBoard[row][col] = true
               count += nQueen(boolArrBoard,row+1)
				if(count) return 1;
               boolArrBoard[row][col] = false
           }
       }
       return count
   }
   
   function isSafe(boolArrBoard,row,col){
       //vertical*
       for(let i = 0; i < row; i++){
          if(boolArrBoard[i][col]){
           return false
          }
       }
   
       //left diagonal*
       let maxLeft = Math.min(row,col)
       for(let i = 1; i <= maxLeft; i++){
           if(boolArrBoard[row - i][col - i]){
               return false
              }
       }
   
       //right diagonal*
       let maxRight = Math.min(row, boolArrBoard.length - col - 1)
       for(let i = 1; i <= maxRight; i++){
           if(boolArrBoard[row - i][col + i]){
               return false
              }
       }
   
       return true
   }
   function display(boolArrBoard){
	let div = document.getElementById("solution");
	div.innerHTML = "";
       for( let row in boolArrBoard){
           for(let column in boolArrBoard[row]){
               if(boolArrBoard[row][column]){
                   div.append('O ')
               }
               else{
                   div.append('+ ')
               }
           }
           div.append('\n')
       }
   }

function shuffle(array) {
  let currentIndex = array.length;

  // While there remain elements to shuffle...
  while (currentIndex != 0) {

    // Pick a remaining element...
    let randomIndex = Math.floor(Math.random() * currentIndex);
    currentIndex--;

    // And swap it with the current element.
    [array[currentIndex], array[randomIndex]] = [
      array[randomIndex], array[currentIndex]];
  }
}

var indexes;
function generate() {
   let n = 10
   let boolArrBoard = Array.from({length: n}, () => {
       return new Array(n).fill(false)
   })
   indexes = Array(n).fill().map((x,i)=>i)
   shuffle(indexes);
   nQueen(boolArrBoard,0)
}
</script>
<pre id="solution"></pre>
<button onclick="generate()">¡Generar!</button>
<script>
generate();
</script>