dp2-v1

class Solution {
public:
    /**
     * @param n: An integer
     * @return: An integer
     */
    int climbStairs(int n) {
        // write your code here
        int dp[n+1];
        dp[0] = 0;
        dp[1] = 1;
        dp[2] = 2;
        
        for(int i=3;i<=n;i++)
         dp[i] = dp[i-1] + dp[i-2];
         
        return dp[n];
    }
};