LeetCode OJ——Climbing Stairs

http://oj.leetcode.com/problems/climbing-stairs/

走台阶的题目，转换出数学模型之后，就是Fibonacci数列。后一个数等于前两个数的和。

递归版本超时，代码如下：

class Solution {
public:
    int walk(int sum)
    {
        if(sum == 0 )
            return 1;
        if(sum ==1)
            return 1;
        return walk(sum-1)+walk(sum-2);
    }


    int climbStairs(int n) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        return walk(n);
    }
};

然后改成顺序的了，AC，代码如下：

#include <iostream>

using namespace std;

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* arr = (int*)malloc(sizeof(int)*(n+2));
        arr[0] = 1;
        arr[1] = 1;

        for(int i = 2;i<=n;i++)
            arr[i] = arr[i-1]+arr[i-2];
        return arr[n];
    }
};


int main()
{
    Solution myS;
    int ans = myS.climbStairs(25);

    cout<<ans<<endl;
    
    return 0;
}

加油！