题目描述
大家都知道斐波那契数列,现在要求输入一个整数n,请你输出斐波那契数列的第n项(从0开始,第0项为0)。
n<=39
C++11(clang++ 3.9)
class Solution { public: int Fibonacci(int n) { // f(0) = 0 // f(1) = 1 // f(2) = f(1) + f(0) // ... // f(n-2) = f(n-3) + f(n-4) // f(n-1) = f(n-2) + f(n-3) // f(n) = f(n-1) + f(n-2) if(n <= 0) return 0; if(n == 1) return 1; int small = 0; int large = 1; int ret = 0; for(int i = 0; i < n - 1; i++) { ret = large + small; small = large; large = ret; } return ret; } };