sudokusolve.js

// This code solves a puzzle on websudoku.com
// You can make a javascript bookmark by creating a bookmark and entering
// javascript:var script = document.createElement('script'), head = document.getElementsByTagName("head")[0];script.src = "https://gist.github.com/showercurtain/ea82c3a725b64ab4a534e39adcd97b0c.js"; head.appendChild(script);
// as the url.
// It's not working yet

function getusable(board,pos) {
	var unusable = [""];
	for (let i = 0;i < 9;i++) {
		if (!(unusable.includes(board[i+(pos[1]*9)].value))){
			unusable.push(board[i+(pos[1]*9)].value);
		}
		if (!(unusable.includes(board[(i*9)+pos[0]].value))){
			unusable.push(board[(i*9)+pos[0]].value);
		}
		pos2 = [(Math.floor(pos[0]/3)*3)+(i%3),(Math.floor(pos[1]/3)*3)+Math.floor(i/3)];
		if (!(unusable.includes(board[pos2[0]+(9*pos2[1])].value))){
			unusable.push(board[pos2[0]+(9*pos2[1])].value);
		}
	}
	var usable = [];
	for (let i = 1;i < 10;i++) {
		if (!(unusable.includes(String(i)))) {
			usable.push(String(i));
		}
	}
	return usable;
}

function getempty(board) {
	var empty = [];
	for (let i = 0;i < 9;i++) {
		for (let j = 0;j < 9;j++) {
			if (board[i+(9*j)].value === "") {
				empty.push([i,j]);
			}
		}
	}
	return empty;
}

function solve_recursive(board,empty,start) {
	let usable = getusable(board,empty[start]);
	if ((empty.length === 1) & (usable.length === 1)) {
		board[empty[start][0]+(empty[start][1]*9)].value = usable[0];
		return true;
	}
	for (let i = 0;i < usable.length;i++) {
		board[empty[start][0]+(empty[start][1]*9)].value = usable[i];
		if (solve_recursive(board,empty,start+1)) {return true;}
	}
	board[empty[start][0]+(empty[start][1]*9)].value = "";
	return false;
}

function solve() {
	inps = document.getElementById("puzzle_grid").getElementsByTagName("input")
	solve_recursive(inps,getempty(inps),0)
}