Fibonacci sequence of C + + algorithm

Title: Write a function, enter N, and find the nth of the Fibonacci sequence.

Method 1: Recursion:

int fib2 (int n) {if (n = = 0)  return 0;if (n = = 1)  return 1;return fib2 (n-1) +fib2 (n-2);}

Cons: If n is large, then the degree of recursion is more deep

Method 2:

int fib (int n) {int result[2] = {0,1};if (n < 2) return result[n];int Fibone = 0;int fibtwo = 1;int fibn   = 0;int i = 0 ; for (i = 2; I <= n; i++) {fibn = Fibone + fibtwo;fibone = Fibtwo;fibtwo = fibn;} return fibn;}

The infinite recursion problem is avoided, and a cycle time complexity is O (n);

Fibonacci sequence of C + + algorithm