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?

Note: Given n will be a positive integer.

解题思路：

我们算出到第m（0 < m ≤ n）步的走法并把它存到一个数组step里，由于每次只能走1或2步，这样到达第n 步的方法则为到达第n-1步和第n-2步的方法的和。

代码：

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