[C]fibonacci series, recursion, time.h

//使用recursion来计算生成fibonacci series前49个数,并计算程序运行时间
#include <stdio.h>
#include <time.h>
double fibon(int n) {
    if (n == 1 || n == 2)
        return 1;
    else if (n > 2)
        return fibon(n-1) + fibon(n-2);
    else return 0;
}

int main() {
    double t = time(NULL); //纪录开始时间
    for (int i = 1; i < 50; i++) {
        printf("%f
", fibon(i));
    }
    double elapsed = time(NULL) - t; //计算运行时间
    printf("It took %f seconds to finish.
", elapsed);
    return 0;
}