【题解】【DP】【Leetcode】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?

思路：

最简单的DP问题：递归+查表

代码:

 int climbStairs(int n) {

     vector<int> memo(n+, -);//忘了在memo[0]没有意义的时候，数组初始大小加一。。。

     return climb(n, memo);

 }

 int climb(int n, vector<int>& memo){//忘了加&，就会Time Limit Exceeded

     if(n < ){

         return -;

     }

     else if(n <= ){

         memo[n] = n;

         return n;

     }

     if (memo[n-] == -)

         memo[n-] = climb(n-, memo);//修改了递归函数名之后没有更改其他函数体中的引用

     if(memo[n-] == -)

         memo[n-] = climb(n-, memo);

     //return memo[n-1] + 2*memo[n-2];//等等，子问题中好像有重叠

     return memo[n-] + memo[n-];

 }