LeetCode 650 2 Keys Keyboard - LeetCode Weekly Contest 43

题目：

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'.

Example 1:

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'.

Note:

The 

n

 will be in the range [1, 1000].

题意：
初始字符串为“A”，只有两种操作允许：

Copy All：把当前所有的字符复制
Paste：把最后一次复制的字符串粘贴
问最少经过多少步可以把初始字符串变成给定 n 个’A'的字符串。
n的范围是 [1, 1000]

可以当作模拟来做，对于每次都有两种情况，复制和粘贴，分别进行模拟。
尝试过dp，没改出来，，差点火候，还是要练习啊

代码如下：

class Solution {
public:
int ans = 999999999;
void dfs(int now, int copy, int step, int n) {
if (now == n) {
ans = min(ans, step);
}
else if (now > n) return;
if (copy != 0)
dfs(now + copy, copy, step + 1, n);
if (now != copy)
dfs(now, now, step + 1, n);
}
int minSteps(int n) {
dfs(1, 0, 0, n);
return ans;
}
};