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?

Note: Given n will be a positive integer.

Example 1:

Input: 2Output:  2Explanation:  There are two ways to climb to the top.1. 1 step + 1 step2. 2 steps

Example 2:

Input: 3Output:  3Explanation:  There are three ways to climb to the top.1. 1 step + 1 step + 1 step2. 1 step + 2 steps3. 2 steps + 1 step

斐波那契数列。程序如下所示：

class Solution {    public int climbStairs(int n) {        int[] steps = new int[n];        if (n <= 2){            return n;        }        steps[0] = 1;        steps[1] = 2;        for (int i = 2; i < n; ++ i){            steps[i] = steps[i-1] + steps[i-2];        }        return steps[n-1];    }}