【递归练习】算24点

最新推荐文章于 2022-03-29 13:16:19 发布

原创最新推荐文章于 2022-03-29 13:16:19 发布 · 2.1k 阅读

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代码

#include <cstdio>
#include <cmath>
#define EPS 1e-8
using namespace std;

double a[4];

bool judge(double a[], int n)
{
    if (n == 1){
        if (fabs(a[0]-24) <= EPS) return 1;
        else return 0;
    }
    double b[4];
    for (int i = 0; i < n-1; ++i)
        for (int j = i+1; j < n; ++j){
            int rem = 0;
            for (int k = 0; k < n; ++k)
                if (k != i && k != j) b[rem++] = a[k];
            b[rem] = a[i] + a[j];
            if (judge(b, rem+1)) return 1;
            b[rem] = a[i] - a[j];
            if (judge(b, rem+1)) return 1;
            b[rem] = a[j] - a[i];
            if (judge(b, rem+1)) return 1;
            b[rem] = a[i] * a[j];
            if (judge(b, rem+1)) return 1;
            if (fabs(a[j]) > EPS){
                b[rem] = a[i] / a[j];
                if (judge(b, rem+1)) return 1;
            }
            if (fabs(a[i]) > EPS){
                b[rem] = a[j] / a[i];
                if (judge(b, rem+1)) return 1;
            }
        }
    return 0;
}

int main()
{
    while(~scanf("%lf%lf%lf%lf", &a[0], &a[1], &a[2], &a[3]) &&
          (a[0] || a[1] || a[2] || a[3]))
            judge(a, 4) ? printf("YES\n"): printf("NO\n");
    return 0;
}