ClimbingStairs(leetcode)

题目：
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?

题解：

public static int climbStairs(int n) {   if(n<=3) {      return n;   }   int []dp=new int [n+1];   dp[1]=1;   dp[2]=2;   for(int i=3;i<n+1;i++) {     dp[i]=dp[i-1]+dp[i-2];   }   return dp[n];}