剑指offer 7. 斐波那契数列 & leetcode 剑指 Offer 10- I. 斐波那契数列

 1 class Solution {
 2     public int fib(int n) {
 3         if(n == 0 || n == 1){   // 边界值
 4             return n;
 5         }
 6         int a = 1, b = 0, sum = 0;  // 进入迭代
 7         for(int i = 2; i <= n; i++){
 8             sum = (a + b) % 1000000007;
 9             b = a;
10             a = sum;
11         }
12         return sum;
13     }
14 }

 1 class Solution {
 2     public int fib(int n) {
 3         
 4         int a = 0, b = 1, sum = 0;  // 进入迭代
 5         for(int i = 0; i < n; i++){
 6             sum = (a + b) % 1000000007;
 7             a = b;
 8             b = sum;
 9         }
10         return a;
11     }
12 }