Leetcode: Climbing Stairs

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

class Solution {public:    int dp[10000];    int DP(int n){        if(dp[n]<0) dp[n]=DP(n-1)+DP(n-2);        return dp[n];    }    int climbStairs(int n) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        memset(dp,-1,sizeof(dp));        dp[0]=1;        return DP(n);    }};