湖南多校对抗赛（2015.05.03）Problem A: Twenty-four point

给四个数 问能不能算出24点。。。我的方法比较烂。。。920ms 差点TLE。应该有更好的方法。

 

#include<stdio.h>

#include<string.h>

#include<math.h>

#include<algorithm>

using namespace std;

double a[5], ff[5], n;

double rt[30][5], yy[5];

int sum;

double get(double x, double y, int fu)

{

    if (fu == 1) return x + y;

    if (fu == 2) return x - y;

    if (fu == 3) return x * y;

    if (fu == 4) return x / y;

}

void dfs(int tot)

{

    int ii;

    if (tot == 4)

    {

        rt[sum][1] = yy[0];

        rt[sum][2] = yy[1];

        rt[sum][3] = yy[2];

        rt[sum][4] = yy[3];

        sum++;

        return;

    }

    for (ii = 0; ii < 4; ii++)

    {

        if (ff[ii] == 0)

        {

            ff[ii] = 1;

            yy[tot] = a[ii];

            dfs(tot + 1);

            ff[ii] = 0;

        }

    }

}

int main()

{

    while (~scanf("%lf%lf%lf%lf", &a[0], &a[1], &a[2], &a[3]))

    {

        memset(ff, 0, sizeof(ff));

        sum = 1; dfs(0); int i, j, k, g;

        int ans = 0;

        double linshi1 = 0, linshi2 = 0, linshi3 = 0;

        double z, x, c, v;

        for (i = 1; i <= 24; i++)

        {

            for (g = 1; g <= 4; g++)

            {

                for (k = 1; k <= 4; k++)

                {

                    for (j = 1; j <= 4; j++)

                    {

                         

                        z = rt[i][1]; x = rt[i][2]; c = rt[i][3]; v = rt[i][4];

                        linshi1 = get(z, x, g);

                        linshi2 = get(linshi1, c, k);

                        linshi3 = get(linshi2, v, j);

                        if (fabs(linshi3 - 24)<0.0000001){ ans = 1; break; }

 

                         

                        linshi1 = get(z, x, g);

                        linshi2 = get(c, v, j);

                        linshi3 = get(linshi1, linshi2, k);

                        if (fabs(linshi3 - 24)<0.0000001){ ans = 1; break; }

 

                         

                        linshi1 = get(x, c, k);

                        linshi2 = get(z, linshi1, g);

                        linshi3 = get(linshi2, v, j);

                        if (fabs(linshi3 - 24)<0.0000001){ ans = 1; break; }

 

                         

                        linshi1 = get(x, c, k);

                        linshi2 = get(linshi1, v, j);

                        linshi3 = get(z, linshi2, g);

                        if (fabs(linshi3 - 24)<0.0000001){ ans = 1; break; }

 

                         

                        linshi1 = get(c, v, j);

                        linshi2 = get(z, x, g);

                        linshi3 = get(linshi1, linshi2, k);

                        if (fabs(linshi3 - 24)<0.0000001){ ans = 1; break; }

 

                         

                        linshi1 = get(c, v, j);

                        linshi2 = get(x, linshi1, k);

                        linshi3 = get(z, linshi2, g);

                        if (fabs(linshi3 - 24)<0.0000001){ ans = 1; break; }

 

                    }

                    if (ans) break;

                }

                if (ans) break;

            }

            if (ans) break;

        }

        if (ans == 1)printf("Yes\n");

        else printf("No\n");

    }

    return 0;

}