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?

class Solution {
public:
    int climbStairs(int n) {
    /* 给定一个数n，有两种途径到达n
     一，从n-1处，爬一阶楼梯到达n
     二，从n-2处，爬两阶楼梯到达n*/
     if (n==0)
     return 0;
     if (n==1)
     return 1;
     if (n==2)
     return 2;
     //int  *step = new int [n+1];动态申请数组的两种方式
     vector <int>step(n+1);
     if(n>2)
     {
      step[0] = 0;
      step[1] = 1;
      step[2] = 2;
      for (int i= 3;i<=n;i++)
      step[i] = step[i-1] +step[i-2] ;
      return step[n];
     }
       
    }
};