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[leetcode] 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?

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

 

分析:Fibonacci数列,不要用递推,重复计算太多,用DP。

public class Solution {    public int climbStairs(int n) {        if(n<=0)            return 0;        if(n==1)            return 1;        if(n==2)            return 2;                int i;        int firstWays=1;        int secondWays=2;        int ways=0;        for(i=3;i<=n;i++){            ways=firstWays+secondWays;            firstWays=secondWays;            secondWays=ways;        }                return ways;                }}
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