先举个例子，我不知道这个例子有没有答案哈：

a + b * c / d + e - f - g + 12 / 8 * h / i = 10
请把a~i填入1-9这9个数字，使用等式成立。9个变量对应9个数字，必须是一对一的。这种题蛮伤脑筋的，所以，用枚举来搞定算了！

看看代码：

var a,b,c,d,e,f,g,h,i;var res = 0;for(a=1;a<=9;a++){
    for(b=1;b<=9;b++){
        if( b == a ) continue;
        for(c=1;c<=9;c++){
            if( c == a ) continue;
            if( c == b ) continue;
            for(d=1;d<=9;d++){
                if( d == a ) continue;
                if( d == b ) continue;
                if( d == c ) continue;
                for(e=1;e<=9;e++){
                    if( e == a ) continue;
                    if( e == b ) continue;
                    if( e == c ) continue;
                    if( e == d ) continue;
                    for(f=1;f<=9;f++){
                        if( f == a ) continue;
                        if( f == b ) continue;
                        if( f == c ) continue;
                        if( f == d ) continue;
                        if( f == e ) continue;
                        for(g=1;g<=9;g++){
                            if( g == a ) continue;
                            if( g == b ) continue;
                            if( g == c ) continue;
                            if( g == d ) continue;
                            if( g == e ) continue;
                            if( g == f ) continue;
                            for(h=1;h<=9;h++){
                                if( h == a ) continue;
                                if( h == b ) continue;
                                if( h == c ) continue;
                                if( h == d ) continue;
                                if( h == e ) continue;
                                if( h == f ) continue;
                                if( h == g ) continue;
                                for(i=1;i<=9;i++){
                                    if( i == a ) continue;
                                    if( i == b ) continue;
                                    if( i == c ) continue;
                                    if( i == d ) continue;
                                    if( i == e ) continue;
                                    if( i == f ) continue;
                                    if( i == g ) continue;
                                    if( i == h ) continue;res = a + b;res = res * c;if(res % d != 0) continue;res = res / d;if(res < 0) continue;res = res - e;if(res < 0) continue;res = res + f;res = res * 10;res = res - 43;if(res < 0) continue;res = res / 11;res = res + 12;res = res - g;if(res < 0) continue;res = res * h;if(res % h != 0) continue;res = res / i;if( res == 20 ){
    console.log([a,b,c,d,e,f,g,h,i]);}

                                }
                            }
                        }
                    }
                }
            }
        }
    }}

代码写得可能很糟糕，不简练，但大概意思是对的。有几点要注意的：

1、每个数字不一样。所以枚举的时候，遇到当前变量等于之前的变量时，要跳出当前循环。
2、遇到除法，则必须整除。