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：

简单的递归，ways[n] = ways[n - 1] + ways[n - 2];

class Solution {public:    int climbStairs(int n) {        // IMPORTANT: Please reset any member data you declared, as        // the same Solution instance will be reused for each test case.        int *ways = new int[n + 1];        ways[0] = 0;        ways[1] = 1;        ways[2] = 2;        for(int i = 3;i <= n;i++)            ways[i] = ways[i - 1] + ways[i - 2];          return ways[n];    }};