Climbing Stairs <LeetCode>

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?

 

1:下面用的是递归的方法，但是会超时

 

class Solution {
public:
    int total_steps=0;
    int climbStairs(int n) {
        if(n==0)
        {
            total_steps++;
        }
        else
        {
            if(n>=1)
            {
               climbStairs(n-1);
            }
            if(n>=2)
            {
               climbStairs(n-2);
            }
        }
        return total_steps;
    }
};

 

 

2:用动态规划，解决了问题，代码如下：

 

class Solution {
public:
    int total_steps=0;
    int climbStairs(int n) {
    if(n==1)   return 1;
    if(n==2)   return 2;
    int solutions[1000];
    solutions[0]=0;
    solutions[1]=1;
    solutions[2]=2;
    int i=3;
    while(i<=n)
    {
        solutions[i]=solutions[i-1]+solutions[i-2];
        i++;
    }
    return solutions[n];
    }
};