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?

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这个题面试题还是比较常见的

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原理：

This problem is a Fibonacci problem. F(n)=F(n-1)+F(n-2); Solving this problem by recursion ,we will do a lot of same recursion. Example: F(10)=F(9)+F(8); F(9)=F(8)+F(7); we calculate F(8) twice,when n is large,this will increase as a rate of n's exponent.

So a more efficient way to solve this problem is from Bottom to Top. Calculate F(0) ,F(1); then F(2).........

人生ac最快的代码：

class Solution {public:    int climbStairs(int n)    {                int stepone = 0;        int steptwo = 1;        int sum = 0;                for(int i = 0;i

DP算法求解：

简洁的代码：

递归：

python：