JavaScript之破解数独（附详细代码）
在上一篇分享中，我们用Python和Django来破解数独，这对不熟悉Python和Django的人来说是非常不友好的。这次，笔者只用HTML和JavaScript写了破解数独的程序，对于熟悉前端的人，这是十分友好的。
话不多说，直接上代码。
首页index.html的代码如下：
<html>
<head>
<link rel="stylesheet" type="text/css" href="mystyle.css" />
<script type="text/javascript" src="answer.js"></script>
</head>
<body background="mountain.jpg">
<center><h1>Solve A Sudoku</h1></center>
<table class="sd" border="0" align="center" cellspacing="1" cellpadding="1">
<tr>
<td class="xx"><input id="1" class="big" maxlength="1"></td>
<td class="xx"><input id="2" class="big" maxlength="1"></td>
<td class="rr"><input id="3" class="big" maxlength="1"></td>
<td class="xx"><input id="4" class="big" maxlength="1"></td>
<td class="xx"><input id="5" class="big" maxlength="1"></td>
<td class="rr"><input id="6" class="big" maxlength="1"></td>
<td class="xx"><input id="7" class="big" maxlength="1"></td>
<td class="xx"><input id="8" class="big" maxlength="1"></td>
<td class="xx"><input id="9" class="big" maxlength="1"></td>
</tr>
<tr>
<td class="xx"><input id="10" class="big" maxlength="1"></td>
<td class="xx"><input id="11" class="big" maxlength="1"></td>
<td class="rr"><input id="12" class="big" maxlength="1"></td>
<td class="xx"><input id="13" class="big" maxlength="1"></td>
<td class="xx"><input id="14" class="big" maxlength="1"></td>
<td class="rr"><input id="15" class="big" maxlength="1"></td>
<td class="xx"><input id="16" class="big" maxlength="1"></td>
<td class="xx"><input id="17" class="big" maxlength="1"></td>
<td class="xx"><input id="18" class="big" maxlength="1"></td>
</tr>
<tr>
<td class="xx"><input id="19" class="big" maxlength="1"></td>
<td class="xx"><input id="20" class="big" maxlength="1"></td>
<td class="rr"><input id="21" class="big" maxlength="1"></td>
<td class="xx"><input id="22" class="big" maxlength="1"></td>
<td class="xx"><input id="23" class="big" maxlength="1"></td>
<td class="rr"><input id="24" class="big" maxlength="1"></td>
<td class="xx"><input id="25" class="big" maxlength="1"></td>
<td class="xx"><input id="26" class="big" maxlength="1"></td>
<td class="xx"><input id="27" class="big" maxlength="1"></td>
</tr>
<tr>
<td class="top"><input id="28" class="big" maxlength="1"></td>
<td class="top"><input id="29" class="big" maxlength="1"></td>
<td class="topr"><input id="30" class="big" maxlength="1"></td>
<td class="top"><input id="31" class="big" maxlength="1"></td>
<td class="top"><input id="32" class="big" maxlength="1"></td>
<td class="topr"><input id="33" class="big" maxlength="1"></td>
<td class="top"><input id="34" class="big" maxlength="1"></td>
<td class="top"><input id="35" class="big" maxlength="1"></td>
<td class="top"><input id="36" class="big" maxlength="1"></td>
</tr>
<tr>
<td class="xx"><input id="37" class="big" maxlength="1"></td>
<td class="xx"><input id="38" class="big" maxlength="1"></td>
<td class="rr"><input id="39" class="big" maxlength="1"></td>
<td class="xx"><input id="40" class="big" maxlength="1"></td>
<td class="xx"><input id="41" class="big" maxlength="1"></td>
<td class="rr"><input id="42" class="big" maxlength="1"></td>
<td class="xx"><input id="43" class="big" maxlength="1"></td>
<td class="xx"><input id="44" class="big" maxlength="1"></td>
<td class="xx"><input id="45" class="big" maxlength="1"></td>
</tr>
<tr>
<td class="xx"><input id="46" class="big" maxlength="1"></td>
<td class="xx"><input id="47" class="big" maxlength="1"></td>
<td class="rr"><input id="48" class="big" maxlength="1"></td>
<td class="xx"><input id="49" class="big" maxlength="1"></td>
<td class="xx"><input id="50" class="big" maxlength="1"></td>
<td class="rr"><input id="51" class="big" maxlength="1"></td>
<td class="xx"><input id="52" class="big" maxlength="1"></td>
<td class="xx"><input id="53" class="big" maxlength="1"></td>
<td class="xx"><input id="54" class="big" maxlength="1"></td>
</tr>
<tr>
<td class="top"><input id="55" class="big" maxlength="1"></td>
<td class="top"><input id="56" class="big" maxlength="1"></td>
<td class="topr"><input id="57" class="big" maxlength="1"></td>
<td class="top"><input id="58" class="big" maxlength="1"></td>
<td class="top"><input id="59" class="big" maxlength="1"></td>
<td class="topr"><input id="60" class="big" maxlength="1"></td>
<td class="top"><input id="61" class="big" maxlength="1"></td>
<td class="top"><input id="52" class="big" maxlength="1"></td>
<td class="top"><input id="63" class="big" maxlength="1"></td>
</tr>
<tr>
<td class="xx"><input id="64" class="big" maxlength="1"></td>
<td class="xx"><input id="65" class="big" maxlength="1"></td>
<td class="rr"><input id="66" class="big" maxlength="1"></td>
<td class="xx"><input id="67" class="big" maxlength="1"></td>
<td class="xx"><input id="68" class="big" maxlength="1"></td>
<td class="rr"><input id="69" class="big" maxlength="1"></td>
<td class="xx"><input id="70" class="big" maxlength="1"></td>
<td class="xx"><input id="71" class="big" maxlength="1"></td>
<td class="xx"><input id="72" class="big" maxlength="1"></td>
</tr>
<tr>
<td class="xx"><input id="73" class="big" maxlength="1"></td>
<td class="xx"><input id="74" class="big" maxlength="1"></td>
<td class="rr"><input id="75" class="big" maxlength="1"></td>
<td class="xx"><input id="76" class="big" maxlength="1"></td>
<td class="xx"><input id="77" class="big" maxlength="1"></td>
<td class="rr"><input id="78" class="big" maxlength="1"></td>
<td class="xx"><input id="79" class="big" maxlength="1"></td>
<td class="xx"><input id="80" class="big" maxlength="1"></td>
<td class="xx"><input id="81" class="big" maxlength="1"></td>
</tr>
</table>
<br>
<center>
<button type="button" onclick="clc()">Clear</button>
<button type="button" onclick="get_answer()">Show Answer</button>
</center>
</body>
</html>
其使用的样式表mystyle.css的代码如下：
.sd {
table-layout: fixed;
border: #443 3px solid;
width: 355px;
height: 355px;
background-color: #fff;
vertical-align: middle;
border-collapse: collapse;
text-align: center;
}
.big {
FONT-SIZE: 25px;
border: none;
background-color: transparent;
WIDTH: 30px;
HEIGHT: 30px;
LINE-HEIGHT: 28px;
TEXT-ALIGN: center;
margin: 0px;
COLOR: #0000FF;
FONT-FAMILY: Verdana;
}
td.xx {
border-right: #999 1px solid;
border-top: #999 1px solid;
width: 30px;
height: 30px;
text-align: center;
LINE-height: 30px;
}
td.rr {
border-right: #443 2px solid;
border-top: #999 1px solid;
width: 30px;
height: 30px;
text-align: center;
LINE-height: 30px;
}
td.top {
border-right: #999 1px solid;
border-top: #443 2px solid;
width: 30px;
height: 30px;
text-align: center;
LINE-height: 30px;
}
td.topr {
border-right: #443 2px solid;
border-top: #443 2px solid;
width: 30px;
height: 30px;
text-align: center;
LINE-height: 30px;
}
其使用的JavaScript的代码（answer.js）如下：
//clear all the input
function clc(){
for(var i=0; i<81; i++){
document.getElementsByTagName("input")[i].value = "";
document.getElementsByTagName("input")[i].style.color = 'blue';
}
document.body.style.backgroundImage = "url(mountain.jpg)";
}
//press "show answer" button and show answer then
function get_answer(){
var bool = check_input();
if(bool){
var grid = readAPuzzle();
if(!isValidGrid(grid)){
alert("Invalid input, please try again!");
}
else{
if(search(grid)){
output_ans();
document.body.style.backgroundImage = "url(sky.jpg)";
}
else{
alert("Found no solution!");
}
}
}
}
//check if the input are valid
function check_input(){
var arr = new Array();
for(var i=0; i<81; i++){
arr[i] = Number(document.getElementsByTagName("input")[i].value);
if(isNaN(arr[i])){
alert('Input should be any number between 1 and 9 !');
return false
}
}
if(arr.every(function isZero(x){return x== 0})){
alert('There is no input!');
return false
}
return true
}
//read a puzzle from the web page
function readAPuzzle(){
var arr = new Array();
for(var i=0; i<81; i++){
arr[i] = Number(document.getElementsByTagName("input")[i].value);
}
var grid = new Array();
for(var i=0; i<9; i++){
grid[i] = new Array();
for(var j=0; j<9; j++){
grid[i][j] = 0;
}
}
for(var i=0; i<81; i++){
grid[Math.floor(i/9)][i%9] = arr[i];
}
return grid
}
//Obtain a list of free cells from the puzzle
function getFreeCellList(grid){
var freeCellList = new Array();
index = 0
for(var i=0; i<9; i++){
for(var j=0; j<9; j++){
if(grid[i][j] == 0){
freeCellList[index] = new Array(i,j);
index++;
}
}
}
return freeCellList
}
//Check whether grid[i][j] is valid in the grid
function isValid(i,j,grid){
//Check whether grid[i][j] is valid at the i's row
for(var column=0; column<9; column++){
if((column != j) && (grid[i][column] == grid[i][j])){
return false
}
}
//Check whether grid[i][j] is valid at the j's column
for(var row=0; row<9; row++){
if((row != i) && (grid[row][j] == grid[i][j])){
return false
}
}
//Check whether grid[i][j] is valid at the 3-by-3 box
for(var row=Math.floor(i/3)*3; row < Math.floor(i/3)*3+3; row++){
for(var col=Math.floor(j/3)*3; col < Math.floor(j/3)*3+3; col++){
if((row != i) && (col != j) && (grid[row][col] == grid[i][j])){
return false
}
}
}
return true //The current value at grid[i][j] is valid
}
//Check whether the fixed cells are valid in the grid
function isValidGrid(grid){
for(var i=0; i<9; i++){
for(var j=0; j<9; j++){
if((grid[i][j] < 0) || (grid[i][j] > 9) || ((grid[i][j] != 0) && (! isValid(i,j,grid)))){
return false
}
}
}
return true
}
//Search for a solution
function search(grid){
var freeCellList = getFreeCellList(grid);
var numberOfFreeCells = freeCellList.length;
if(numberOfFreeCells == 0){
return true
}
var k = 0; //Start from the first free cell
while(true){
var i = freeCellList[k][0];
var j = freeCellList[k][1];
if(grid[i][j] == 0){
grid[i][j] = 1;
}
if(isValid(i,j,grid)){
if(k+1 == numberOfFreeCells){
//no more free cells
return true //A solution is found
}
else{
//Move to the next free cell
k++;
}
}
else{
if(grid[i][j] < 9){
//Fill the free cell with the next possible value
grid[i][j]++;
}
else{
//grid[i][j] is 9,backtrack
while(grid[i][j] == 9){
if(k == 0){
return false //No possible value
}
grid[i][j] = 0; //Reset to free cell
k--; //Backtrack to the preceding free cell
i = freeCellList[k][0];
j = freeCellList[k][1];
}
//Fill the free cell with the next possible value
//search continues from this free cell at k
grid[i][j]++;
}
}
}
return true //A solution is found
}
//output the answer on the web page
function output_ans(){
var grid = readAPuzzle();
var grid_original = readAPuzzle();
if(search(grid)){
for(var i=0; i<81; i++){
if(grid[Math.floor(i/9)][i%9] != grid_original[Math.floor(i/9)][i%9]){
document.getElementsByTagName("input")[i].value = grid[Math.floor(i/9)][i%9];
document.getElementsByTagName("input")[i].style.color = 'black';
}
}
}
}
我们将对如何操作做一个简单的图解说明。
开始的页面如下：
