[C]recursion递归计算阶乘

计算阶乘

#include <stdio.h>
double fact(int);
int main()
{
    int x;
    printf("input a positive integer (<20) to calculate its factorial: ");
    scanf("%d", &x);
    printf("Factorial of %d is %.2f\n", x, fact(x));
    return 0;
}

double fact(int x)
{
    if (x == 1)
        return 1;
    else
        return x * fact(x-1);
}

 

 

generate fibonacci series

#include <stdio.h>
double fibon(int);
int main()
{
    for (int i = 1; i <= 20; i++) //生成前20个序列1,1,2,3,5,8...
    {
        printf("%f\n", fibon(i));
    }
    return 0;
}

double fibon(int x)
{
    if (x == 1)
        return 1;
    if (x == 2)
        return 1;
    if (x > 2)
        return fibon(x-1) + fibon(x-2);

}