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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?

1,注意函数  f(n)=f(n-1)+f(n-2)

 

package Leetcode;public class ClimbingStairs {    public int climbStairs(int n) {        if(n<=1){            return n;        }        int before=1;        int beforebefore=1;        int current=0;        for(int i=2;i<=n;i++){            current=before+beforebefore;            beforebefore=before;            before=current;        }        return current;    }}

 

leetcode climbing stairs