爬楼梯问题

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