力扣70-爬楼梯 DP+滚动数组

	因为每次都只能跳两格，所以后面一格等于前面两格之和

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