70. Climbing Stairs#1(Done)

Solution

public class Solution {    public int climbStairs(int n) {        if (n <= 1) {            return 1;        }        int last = 1;        int lastLast = 1;        int ways = 0;        while (n -- > 1) {            ways = last + lastLast;            lastLast = last;            last = ways;        }        return ways;    }}

Problem#1
* 递归算法超出时间限制
* 用迭代
* 公式解法