最最简单的dp

1 class Solution { 2 public: 3     int flag[1000001] = {
   0}; 4     int f(int n) { 5         if (flag[n] != 0) return flag[n]; 6         if (1 == n) { 7             return 1; 8         } else if (2 == n) { 9             return 2;10         } else {11             flag[n] = f(n - 1) + f(n - 2) ;12             return flag[n];13         }14     }15     16     int climbStairs(int n) {17         memset(flag,0, 1000001);18         return f(n);19     }20 };