70. 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?

简单dp

class Solution {
public:
    int dp[1000] = {0};
    int climbStairs(int n) {
        if (dp[n] > 0) return dp[n];
        if (n == 1) return dp[1] = 1;
        else if (n == 2) return dp[2] = 2;
        else return dp[n] = climbStairs(n - 1) + climbStairs(n - 2);
    }
};