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精度问题？上面的样例过不了下面的AC

Posted by allen4053040allen at 2011-08-16 07:28:38 on Problem 2715 and last updated at 2011-08-16 07:36:42

#include<iostream>
#include<cmath>

using namespace std;

#define EPS 0.00001

int main()
{
    double B, W, C;
    while(scanf("%lf%lf%lf", &B, &W, &C) && (B + W + C)) {
        B *= 16, W *= 16;
        double ans = B / (B + W);
        double raW = 0, raB = 1;
        int sum = 0;
        while(fabs(raW - ans) > EPS || fabs(raB - ans) > EPS) {
            raW = 1 - (W * (1 - raW) + C * (1 - raB)) / (C + W);
            raB = ((B - C) * raB + C * raW) / B;
            sum ++;
        }
        printf("%d\n", sum);
    }
}



/*****/
#include<iostream>
#include<cmath>

using namespace std;

#define EPS 0.00001

int main()
{
    double B, W, C;
    while(scanf("%lf%lf%lf", &B, &W, &C) && (B + W + C)) {
        B *= 16, W *= 16;
        double ans = B / W;
        double raW = 0, raB = 1;
        int sum = 0;
        while(fabs(raW / (1 - raW) - ans) > EPS || fabs(raB / (1 - raB) - ans) > EPS) {
            raW = 1 - (W * (1 - raW) + C * (1 - raB)) / (C + W);
            raB = ((B - C) * raB + C * raW) / B;
            sum ++;
        }
        printf("%d\n", sum);
    }
}

Followed by:

貌似前者是精度丢失问题，但这样的话递推也一样的吧。。。求大牛递推代码 (16) allen4053040allen 2011-08-16 07:45:22

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Content:

> #include<iostream>
> #include<cmath>
> 
> using namespace std;
> 
> #define EPS 0.00001
> 
> int main()
> {
>     double B, W, C;
>     while(scanf("%lf%lf%lf", &B, &W, &C) && (B + W + C)) {
>         B *= 16, W *= 16;
>         double ans = B / (B + W);
>         double raW = 0, raB = 1;
>         int sum = 0;
>         while(fabs(raW - ans) > EPS || fabs(raB - ans) > EPS) {
>             raW = 1 - (W * (1 - raW) + C * (1 - raB)) / (C + W);
>             raB = ((B - C) * raB + C * raW) / B;
>             sum ++;
>         }
>         printf("%d\n", sum);
>     }
> }
> 
> 
> 
> /*****/
> #include<iostream>
> #include<cmath>
> 
> using namespace std;
> 
> #define EPS 0.00001
> 
> int main()
> {
>     double B, W, C;
>     while(scanf("%lf%lf%lf", &B, &W, &C) && (B + W + C)) {
>         B *= 16, W *= 16;
>         double ans = B / W;
>         double raW = 0, raB = 1;
>         int sum = 0;
>         while(fabs(raW / (1 - raW) - ans) > EPS || fabs(raB / (1 - raB) - ans) > EPS) {
>             raW = 1 - (W * (1 - raW) + C * (1 - raB)) / (C + W);
>             raB = ((B - C) * raB + C * raW) / B;
>             sum ++;
>         }
>         printf("%d\n", sum);
>     }
> }
>

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精度问题？上面的样例过不了 下面的AC

精度问题？上面的样例过不了下面的AC