24点求解器

\(24\) 点求解器，输出任意一组解。

#include <bits/stdc++.h>
using namespace std;

#define to_st to_string
#define in push_back
typedef double db;
typedef string st;

vector<pair<db,st>>Number;
int A,B,C,D;
bool Out;

void Output(){Out=true;puts("Possble!");cout<<Number[0].second<<"=24\n";}
void DFS(int step);

void Add(db A,st AA){Number.clear();Number.in({A,AA});}
void Add(db A,db B,st AA,st BB){Number.clear();Number.in({A,AA});Number.in({B,BB});}
void Add(db A,db B,db C,st AA,st BB,st CC){Number.clear();Number.in({A,AA});Number.in({B,BB});Number.in({C,CC});}
void Add(db A,db B,db C,db D,st AA,st BB,st CC,st DD){Number.clear();Number.in({A,AA});Number.in({B,BB});Number.in({C,CC});Number.in({D,DD});}

st Text(st A,char c,st B){
    return '('+A+c+B+')';
}

void Calc(db A,db B,st AA,st BB){
    Add(A+B,Text(AA,'+',BB));DFS(1);
    Add(A-B,Text(AA,'-',BB));DFS(1);
    Add(A*B,Text(AA,'*',BB));DFS(1);
    if(B!=0){Add(A/B,Text(AA,'/',BB));DFS(1);}
}

void Calc(db A,db B,db C,st AA,st BB,st CC){
    Add(A+B,C,Text(AA,'+',BB),CC);DFS(2);
    Add(A-B,C,Text(AA,'-',BB),CC);DFS(2);
    Add(A*B,C,Text(AA,'*',BB),CC);DFS(2);
    if(B!=0){Add(A/B,C,Text(AA,'/',BB),CC);DFS(2);}
}

void Calc(db A,db B,db C,db D,st AA,st BB,st CC,st DD){
    Add(A+B,C,D,Text(AA,'+',BB),CC,DD);DFS(3);
    Add(A-B,C,D,Text(AA,'-',BB),CC,DD);DFS(3);
    Add(A*B,C,D,Text(AA,'*',BB),CC,DD);DFS(3);
    if(B!=0){Add(A/B,C,D,Text(AA,'/',BB),CC,DD);DFS(3);}
}

void DFS(int step){
    if(Out) return;
    if(step==1 and 23.9<Number[0].first and Number[0].first<24.1){
        Output();
    }else{
        if(step==2){
            db A=Number[0].first;
            db B=Number[1].first;
            st AA=Number[0].second;
            st BB=Number[1].second;
            Calc(A,B,AA,BB);
            Calc(B,A,BB,AA);
        }else if(step==3){
            db A=Number[0].first;
            db B=Number[1].first;
            db C=Number[2].first;
            st AA=Number[0].second;
            st BB=Number[1].second;
            st CC=Number[2].second;
            Calc(A,B,C,AA,BB,CC);Calc(A,C,B,AA,CC,BB);
            Calc(B,A,C,BB,AA,CC);Calc(B,C,A,BB,CC,AA);
            Calc(C,A,B,CC,AA,BB);Calc(C,B,A,CC,BB,AA);
        }else if(step==4){
            db A=Number[0].first;
            db B=Number[1].first;
            db C=Number[2].first;
            db D=Number[3].first;
            st AA=Number[0].second;
            st BB=Number[1].second;
            st CC=Number[2].second;
            st DD=Number[3].second;
            Calc(A,B,C,D,AA,BB,CC,DD);Calc(A,C,B,D,AA,CC,BB,DD);Calc(A,D,B,C,AA,DD,BB,CC);
            Calc(B,A,C,D,BB,AA,CC,DD);Calc(B,C,A,D,BB,CC,AA,DD);Calc(B,D,A,C,BB,DD,AA,CC);
            Calc(C,A,B,D,CC,AA,BB,DD);Calc(C,B,A,D,CC,BB,AA,DD);Calc(C,D,A,B,CC,DD,AA,BB);
            Calc(D,A,B,C,DD,AA,BB,CC);Calc(D,B,A,C,DD,BB,AA,CC);Calc(D,C,A,B,DD,CC,AA,BB);
        }
    }
}

void Main()
{
    srand(time(0));
    printf(">>> ");
    scanf("%d%d%d%d",&A,&B,&C,&D);
    Add(A,B,C,D,to_st(A),to_st(B),to_st(C),to_st(D));
    Out=false;
    DFS(4);
    if(!Out){
        puts("Impossble...QwQ");
    }puts("");
}

int main()
{
    while(true){
        Main();
    }
    return 0;
}