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：

开始页面

首先，如果没有任何输入而直接点击“Show Answer”按钮，则会显示如下页面：

没有任何输入而直接点击“Show Answer”按钮

如何在表格中一旦输入非数字，则会显示如下页面：

在表格中输入非数字

若在九宫格中输入的数字不符合规则，则会显示页面如下：

在九宫格中输入的数字不符合规则

当我们输入的数字符合规则时，就能得到正确的答案，比如，我们在http://www.cn.sudokupuzzle.org/上随便找一个“骨灰级”的数独并输入，页面如下：

“骨灰级”的数独

当我们按下“Show Answer”按钮时，显示的答案如下：

显示答案

当按下“Clear”按钮时，所有格子将会被清空，这样我们就能就行下一次破解啦~~
本次分享到此结束，欢迎大家交流~~
P.S.写这个项目主要是为了学习JavaScript,因为最近刚开始接触前端。欢迎大家访问这个项目的Github地址：https://github.com/percent4/Sudoku-Solver-JavaScript-Version .

JavaScript之破解数独（附详细代码）

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