***求2/1,3/2,5/3,8/5,13/8,21/13,.....前20项之和。请改正程序中的错误，使它能得出正确的结果

题目中错误的解法 

#include <stdio.h>
main()
{
    int i, s1 = 2, s2 = 1;
    float x, sum = 0;

    for (i = 1; i <= 20; i++)
    {
        sum += s1 / s2;
        x = s1;
        s1 += s2;
        s2 = x;
    }
    printf("sum = %9.6f\n", sum);
}

 

已知的正确解法

#include<stdio.h>
int main()
{
    int i;
    double a = 1.0, b = 2.0, sum = 0, c = 0, d = 0;
    for(i = 1; i <= 20; i++)
    {
        c = b / a;
        sum += c;
        d = a + b;
        a = b;
        b = d;
    }
    printf("The sum is:\n%lf\n", sum);
    return 0;
}