Java [Leetcode 70]Climbing Stairs

题目描述：

You are climbing a stair case. It takes n steps to reach to the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

解题思路：

利用DP的方法，一个台阶的方法次数为1次，两个台阶的方法次数为2个。n个台阶的方法可以理解成上n-2个台阶，然后2步直接上最后一步；或者上n-1个台阶，再单独上一步。

代码如下：

public class Solution {
    public int climbStairs(int n) {
        int p2 = 1, p1 = 2, current = 0;
        if(n <= 2)
        	return n;
        for(int  i = 2; i < n; i++){
        	current = p2 + p1;
        	p2 = p1;
        	p1 = current;
        }
        return current;
    }
}