leetcode dp题目：

1. 2 Keys Keyboard：
   Initially on a notepad only one character ‘A’ is present. You can perform two operations on this notepad for each step:

Copy All: You can copy all the characters present on the notepad (partial copy is not allowed).
Paste: You can paste the characters which are copied last time.
Given a number n. You have to get exactly n ‘A’ on the notepad by performing the minimum number of steps permitted. Output the minimum number of steps to get n ‘A’.

Input: 3
Output: 3
Explanation:
Intitally, we have one character ‘A’.
In step 1, we use Copy All operation.
In step 2, we use Paste operation to get ‘AA’.
In step 3, we use Paste operation to get ‘AAA’.

难度中等吧:

class Solution {public:    int minSteps(int n) {      //动态规划      //要点 1.dp[0] = dp[1] = 0;      //状态转移方程 ; dp[x] = min(dp[x],dp[y]+y/x)        vector<int> dp(n+1,INT_MAX);        dp[0] = 0,dp[1] = 0;        for(int i=2; i <=n ; i++)        {            for(int j=1; j < i; j++)            {                if(i % j == 0)                {                    dp[i] = min(dp[i],dp[j]+i/j);                }            }        }        return dp[n];    }};