var good = "true"; var bad = "false"; var helpTxt = `Create an algorithm that checks any solved sudoku's validity. Examples: Input.: [ [3, 5, 2, 9, 1, 8, 6, 7, 4], [8, 9, 7, 2, 4, 6, 5, 1, 3], [6, 4, 1, 7, 5, 3, 2, 8, 9], [7, 8, 3, 5, 6, 9, 4, 2, 1], [9, 2, 6, 1, 3, 4, 7, 5, 8], [4, 1, 5, 8, 2, 7, 9, 3, 6], [8, 6, 4, 3, 7, 5, 8, 9, 2], [2, 7, 8, 4, 9, 1, 3, 6, 5], [5, 3, 9, 6, 8, 2, 1, 4, 7] ] Output: false Input: [ [3, 5, 2, 9, 1, 8, 6, 7, 4], [8, 9, 7, 2, 4, 6, 5, 1, 3], [6, 4, 1, 7, 5, 3, 2, 8, 9], [7, 8, 3, 5, 6, 9, 4, 2, 1], [9, 2, 6, 1, 3, 4, 7, 5, 8], [4, 1, 5, 8, 2, 7, 9, 3, 6], [1, 6, 4, 3, 7, 5, 8, 9, 2], [2, 7, 8, 4, 9, 1, 3, 6, 5], [5, 3, 9, 6, 8, 2, 1, 4, 7] ] Output: true `; window.onload = () => { inp.value=`[ [3, 5, 2, 9, 1, 8, 6, 7, 4], [8, 9, 7, 2, 4, 6, 5, 1, 3], [6, 4, 1, 7, 5, 3, 2, 8, 9], [7, 8, 3, 5, 6, 9, 4, 2, 1], [9, 2, 6, 1, 3, 4, 7, 5, 8], [4, 1, 5, 8, 2, 7, 9, 3, 6], [1, 6, 4, 3, 7, 5, 8, 9, 2], [2, 7, 8, 4, 9, 1, 3, 6, 5], [5, 3, 9, 6, 8, 2, 1, 4, 7] ]`; check(); } function checkInp() { if (/[^1-9\[\]\,\s]/.test(inp.value)) return "Wrong symbol"; try { var m = eval (inp.value ); } catch { return "Syntax error"; } if (m.length != 9) return "Number of rows must be 9"; for (let i = 0; i<9; i++) { if (m[i].slice().sort().join("")!=="123456789") return "Error in row " + i; let t = []; for (let j = 0; j<9; j++) t.push(m[j][i]); if (t.sort().join("")!=="123456789") return "Error in column " + i; } for (let i = 0; i<3; i++) for (let j = 0; j<3; j++) { // 3x3 quad[i][j] let t = []; for (let i1 = 0; i1<3; i1++) for (let j1 = 0; j1<3; j1++) t.push(m[i*3+i1][j*3+j1]); if (t.sort().join("")!=="123456789") return `Error in quad[${i}][${j}]` ; } return true; } function check() { let t = checkInp(); res.innerHTML = t === true ? good : bad+"
"+""+t+""; } function help() { alert (helpTxt); }

Simple Sudoku Validator