解24点的算法

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小时候经常玩的小游戏，开发儿童智力==闲着无聊写了个程序，再也不用费脑子啦~

思路如下：

0. 开始的时候想添加括号，加减乘除四种符号进去，但是太麻烦了，作罢。

1.按照正常做法，每次取出两个，有加减乘除四种计算方法，得到的结果和剩下的两个再进行运算，不断地取两个进行运算，直到只剩下一个结果，再与24比较。

2.打印的时候没有想好办法，定义了一个全局变量string r[]存放结果。

代码如下：

#include <iostream>#include <sstream>#include <string>#include "df.h"using namespace std;int num[4]={8,6,2,1};string r[3];void print(){    for(int i=0;i<3;++i){        cout<<r[i]<<endl;    }    cout<<endl;}string trans(double i)//数字转化为string类型，学习了{   ostringstream ost;   ost << i;   string temp(ost.str());   return temp;}double plus(double a,double b){return a+b;}double  minus(double a,double b){return a-b;}double multi(double a,double b){return a*b;}double divi(double a,double b){return a/b;}string makeString(double a,double b,double res,char op){//每一步的结果变成一个算式    string result = trans(a);    result+=op;    result+=trans(b);    result+='=';    result = result+trans(res);    return result;}void process2(double a,double b){    r[2] = makeString(a,b,a+b,'+');    if(a+b==24){        print();    }    r[2] = makeString(a,b,a-b,'-');    if(a-b==24){        print();    }    r[2] = makeString(a,b,a*b,'*');    if(a*b==24){        print();    }    r[2] = makeString(a,b,a/b,'/');    if(a/b==24){        print();    }}void process3(double a0,double a1,double a2){    int a=a0,b=a1;    r[1] = makeString(a,b,a+b,'+');process2(a+b,a2);    r[1] = makeString(a,b,a-b,'-');process2(a-b,a2);    r[1] = makeString(a,b,a*b,'*');process2(a*b,a2);    r[1] = makeString(a,b,a/b,'/');process2(a/b,a2);    a=a0;b=a2;    r[1] = makeString(a,b,a+b,'+');process2(a+b,a1);    r[1] = makeString(a,b,a-b,'-');process2(a-b,a1);    r[1] = makeString(a,b,a*b,'*');process2(a*b,a1);    r[1] = makeString(a,b,a/b,'/');process2(a/b,a1);    a=a1;b=a2;    r[1] = makeString(a,b,a+b,'+');process2(a+b,a0);    r[1] = makeString(a,b,a-b,'-');process2(a-b,a0);    r[1] = makeString(a,b,a*b,'*');process2(a*b,a0);    r[1] = makeString(a,b,a/b,'/');process2(a/b,a0);}void process4(){    int a,b,c,d;    for(int i=0;i<3;++i){        for(int j=i+1;j<4;++j){            a = num[i];            b = num[j];            for(int k=0;k<4;++k){                if(num[k]!=a&&num[k]!=b){                    c=num[k];                    break;                }            }            for(int k=0;k<4;++k){                if(num[k]!=a&&num[k]!=b&&num[k]!=c){                    d=num[k];                    break;                }            }            {                r[0] = makeString(a,b,a+b,'+');process3(a+b,c,d);                r[0] = makeString(a,b,a-b,'-');process3(a-b,c,d);                r[0] = makeString(a,b,a*b,'*');process3(a*b,c,d);                r[0] = makeString(a,b,a/b,'/');process3(a/b,c,d);            }        }    }}int main(){    process4();    return 0;}

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