递归和非递归分别实现求第n个斐波那契数。

递归方法:

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
int fib(int n)
{
	if (n <= 2){
		return 1;
	}
	else{
		return fib(n - 1) + fib(n - 2);
	}
}
int main()
{
	int n = 0;
	printf("enter a number:");
		scanf("%d", &n);
	printf("%d\n", fib(n));
	system("pause");
	return 0;
}

非递归方法:(循环)

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
int main()
{
	int n = 0;
	printf("enter a number:");
		scanf("%d", &n);
		int a = 1;
		int b = 1;
		int c = 1;
		if (n <= 2)
			printf("1");
		for (int i = 0; i < n - 2; i++){
			c = a + b;
			a = b;
			b = c;
		}
		printf("%d", c);
	system("pause");
	return 0;
}