#include <stdio.h> int fac(int x); int main(void) {     int n;     scanf("%d", &n);     if (n == 1 || n == 2)         printf("1\n");     else if (n == 3)         printf("2\n");     else     {         int last = 1;         int sum = 2;         for (int i = 3; i < n; ++i)         {             int temp = sum;             sum = sum + last;             last = temp;         }         printf("循环求出斐波那契序列值:%d\n", sum);     }     int sum2 = fac(n);     printf("递归求出斐波那契序列值:%d\n", sum2);     return 0; } //递归 int fac(int x) {    static int f[50] = {1,1};    if (x == 1 || x == 2)       return f[x-1];    return f[x-1] == 0 ?           ( f[x-1] = fac(x-1) + fac(x-2) ) :           f[x-1] ; }