C语言：分别用while, do-while, for语句编程，求数列前20项之和 2/1, 3/2, 5/3......_用 while 语句和 do-while 语句分别设计程序,计算自然数列 1,2,3……,n 的和,

C语言：分别用while, do-while, for语句编程，求数列前20项之和 2/1, 3/2, 5/3…

while写法：

#include<stdio.h>

int main()
{
    double sum=0, a=2, b=1, c, term;
    int i=1;
    
    while (i<=20)
    {
        term = a/b;
        sum = sum + term;
        c = a+b;
        b = a;
        a = c;
        i++;
    }
    
    printf("The sum is: %.2f\n",sum);
    return 0;
}
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do-while写法：

#include<stdio.h>

int main()
{
    double sum=0, a=2, b=1, c, term;
    int i=1;
    
    do
    {
        term = a/b;
        sum = sum + term;
        c = a+b;
        b = a;
        a = c;
        i++;
    } while (i<=20);

    printf("The sum is: %.2f\n",sum);
    return 0;
}
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for写法：

#include<stdio.h>

int main()
{
    double sum=0, a=2, b=1, c, term;
    int i;
    
    for(i=1; i<=20; i++)
    {
        term = a/b;
        sum = sum + term;
        c = a+b;
        b = a;
        a = c;
    }
    
    printf("The sum is: %.2f\n",sum);
    return 0;
}
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