70. Climbing Stairs

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?

典型的动态规划问题

public class Solution {    public int climbStairs(int n) {        if (n < 1) return 0;        if (n == 1) return 1;        int oneStep = 1, twoStep = 0;          for (int i = 1; i <= n; i++) {            int t = oneStep+twoStep;            twoStep = oneStep;            oneStep = t;        }        return oneStep;    }}