快算24算法，JS版

体验一下，代码如下：

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
<script language="javascript">
function js()
{
    if(!abc())
    {
        document.getElementById("test").innerText = "无解！";
    }
}

function abc()
{
    var x = new Array();
    x[0] = document.getElementById("a").value;
    x[1] = document.getElementById("b").value;
    x[2] = document.getElementById("c").value;
    x[3] = document.getElementById("d").value;

    var a,b,c,d,abN,abcN,abcdN,str,cnt,a1,a2,a3,N;
    str = "";
    cnt = 0;
    abN = 0;
    abcN = 0;
    abcdN = 0;
    N = 0;

    for(var i=0;i<4;i++)
    {
        a = x[i];
        for(var j=0;j<4;j++)
        {
            b = x[j];
            if(j == i)continue;
            for(var m=0;m<4;m++)
            {
                c = x[m];
                if(m == i || m == j)continue;
                for(var n=0;n<4;n++)
                {
                    d = x[n];
                    if(n == i || n == j || n ==m)continue;

                    for(var o=0;o<6;o++)
                    {
                        abN = Com(a,b,o);
                        a1 = ComF(a,b,o);
                        for(var p=0;p<6;p++)
                        {
                            abcN = Com(abN,c,p);
                            a2 = ComF(abN,c,p);
                            for(var q=0;q<6;q++)
                            {
                                abcdN = Com(abcN,d,q);
                                a3 = ComF(abcN,d,q);
                                N = N + 1;
                                if(abcdN==24)
                                {
                                    document.getElementById("test").innerText = a1 + "\n" + a2 + "\n" + a3 + "\n运算次数："+N;
                                    return true;
                                }
                            }
                        }
                    }
                }
            }
        }
    }
    return false;
}

function Com(a,b,OO)
{
    switch (OO){
           case 0:
            return parseFloat(a) + parseFloat(b);
           case 1:
            return parseFloat(a) - parseFloat(b);
           case 2:
            return parseFloat(a) * parseFloat(b);
           case 3:
            return parseFloat(a) / parseFloat(b);
        case 4:
            return parseFloat(b) - parseFloat(a);
        case 5:
            return parseFloat(b) / parseFloat(a);
    }
}

function ComF(a,b,OO)
{
    switch (OO){
       case 0:
            return a + " + " + b + " = " + (parseFloat(a)+parseFloat(b));
       case 1:
            return a + " - " + b + " = " + (parseFloat(a)-parseFloat(b));
       case 2:
            return a + " * " + b + " = " + (parseFloat(a)*parseFloat(b));
       case 3:
            return a + " / " + b + " = " + (parseFloat(a)/parseFloat(b));
       case 4:
            return b + " - " + a + " = " + (parseFloat(b)-parseFloat(a));
       case 5:
            return b + " / " + a + " = " + (parseFloat(b)/parseFloat(a));
    }
}
</script>
</head>

<body>
<p>
  <input name="a" type="text" value="1" />
  <input name="b" type="text" value="2" />
  <input name="c" type="text" value="3" />
  <input name="d" type="text" value="4" />
</p>
<p>
  <input type="button" name="Submit" value="按钮" onclick="js()" />
</p>
<div id=test></div>
</body>
</html>