uva10344-计算23点

#include<stdio.h>
#include<string.h>
//#define LOCAL
const int maxLen = 5;
bool used[maxLen], yes;
int number[maxLen];
char oper[] = {‘+‘,‘-‘,‘*‘};
void Search(int left, int res)
{
    if(left==0 && res!=23) return ;
    else if(left==0 && res==23) { yes=true; return ; }
    for(int i=0; i<maxLen; i++) if(!used[i]){
        for(int k=0; k<3; k++) {
            int mid = res;
            switch(oper[k]) {
                case ‘+‘:{ mid+=number[i]; used[i]=true; break; }
                case ‘-‘:{ mid-=number[i]; used[i]=true; break; }
                case ‘*‘:{ mid*=number[i]; used[i]=true; break; }
                default: break;
            }
            Search(left-1, mid);
            used[i] = false;
        }
    }
}
int main()
{
    #ifdef LOCAL
        freopen("data.txt", "r", stdin);
        freopen("ans.txt", "w", stdout);
    #endif
    bool flag = true;
    for(int i=0; i<maxLen; i++) {
        scanf("%d", &number[i]);
        if(number[i] != 0) flag = false;
    }
    while(!flag) {
        for(int i=0; i<maxLen&&!yes; i++) {
            used[i] = true; 
            Search(maxLen-1, number[i]);
            used[i] = false;
        }
        if(yes) printf("Possible\n");
        else printf("Impossible\n");
        flag = true;
        for(int i=0; i<maxLen; i++) {
            scanf("%d", &number[i]);
            if(number[i] != 0) flag = false;
        }
        memset(used, 0, sizeof(used));
        yes = false;
    }
    return 0;
}