华为机试 24点运算

四个数先从小排序，再全排列（因为全排列的函数需要从小到大先排序）
然后暴力求解

using namespace std;
class Solution {
public:
string is24(string s[4])
{
float num[4],x,y,z;
string X,Y,Z,W;
for(int i=0;i<4;i++)
{
switch(s[i][0])
{
case 'A': num[i] = 1.; break;
case 'K': num[i] = 13.; break;
case 'Q': num[i] = 12.; break;
case 'j': return "ERROR";
case 'J':
if(s[i].length()==1)
{
num[i] = 11.;
break;
}
else
return "ERROR";
case '1':
if(s[i].length()==1)
{
num[i] = 1.;
break;
}
else
{
num[i] = 10.;
break;
}
default :
num[i] =1. + char(s[i][0]) - '1';
}
}

    for(int i=0;i<3;i++)
        for(int j=0;j<3-i;j++)        
            if(num[j]>num[j+1])
                swap(num[j],num[j+1]);    
    do
    {
        for(int i=0;i<4;i++)
        {
            switch(int(num[0]))
            {
                case 1:    W = "A";break;
                case 10: W = "10";break;
                case 11: W = "J";break;
                case 12: W = "Q";break;
                case 13: W = "K";break;
                default:    W = '0' + char(num[0]);
            }
            x = num[0];
            switch(i)
            {
            case 0:    x += num[1];X = W + '+';    break;
            case 1:    x -= num[1];X = W + '-';    break;
            case 2:    x *= num[1];X = W + '*';    break;
            case 3:    x /= num[1];X = W + '/';    break;
            }
            switch(int(num[1]))
            {
                case 1:    X += "A";break;
                case 10: X += "10";break;
                case 11: X += "J";break;
                case 12: X += "Q";break;
                case 13: X += "K";break;
                default:    X += '0' + char(num[1]);
            }
            for(int j=0;j<4;j++)
            {
                switch(j)
                {
                case 0:    y = x+num[2];Y = X + '+';    break;
                case 1:    y = x-num[2];Y = X + '-';    break;
                case 2:    y = x*num[2];Y = X + '*';    break;
                case 3:    y = x/num[2];Y = X + '/';    break;
                }
                switch(int(num[2]))
                {
                    case 1:    Y += "A";break;
                    case 10: Y += "10";break;
                    case 11: Y += "J";break;
                    case 12: Y += "Q";break;
                    case 13: Y += "K";break;
                    default:    Y += '0' + char(num[2]);
                }
                for(int j=0;j<4;j++)
                {
                    switch(j)
                    {
                    case 0:    z = y+num[3];    Z = Y + '+';    break;
                    case 1:    z = y-num[3];    Z = Y + '-';    break;
                    case 2:    z = y*num[3];    Z = Y + '*';    break;
                    case 3:    z = y/num[3];    Z = Y + '/';    break;
                    }
                    switch(int(num[3]))
                    {
                        case 1:    Z += "A";break;
                        case 10: Z += "10";break;
                        case 11: Z += "J";break;
                        case 12: Z += "Q";break;
                        case 13: Z += "K";break;
                        default:    Z += '0' + char(num[3]);
                    }
                    //if(int(z)==24)
                    if(z==24)
                        return Z;                
                }
            }
        }        
    }while(next_permutation(num,num+4));
    return "NONE";   
}

};

int main()
{
Solution A;
string s[4];
for(int i=0;i<4;i++)
{
cin>>s[i];
};
cout<<A.is24(s)<<endl;
// system("pause");
return 0;

}