1487. Making File Names Unique

Given an array of strings names of size n. You will create n folders in your file system such that, at the ith minute, you will create a folder with the name names[i].

Since two files cannot have the same name, if you enter a folder name which is previously used, the system will have a suffix addition to its name in the form of (k), where, k is the smallest positive integer such that the obtained name remains unique.

Return an array of strings of length n where ans[i] is the actual name the system will assign to the ith folder when you create it.

Example 1:

Input: names = ["pes","fifa","gta","pes(2019)"]
Output: ["pes","fifa","gta","pes(2019)"]
Explanation: Let's see how the file system creates folder names:
"pes" --> not assigned before, remains "pes"
"fifa" --> not assigned before, remains "fifa"
"gta" --> not assigned before, remains "gta"
"pes(2019)" --> not assigned before, remains "pes(2019)"

Example 2:

Input: names = ["gta","gta(1)","gta","avalon"]
Output: ["gta","gta(1)","gta(2)","avalon"]
Explanation: Let's see how the file system creates folder names:
"gta" --> not assigned before, remains "gta"
"gta(1)" --> not assigned before, remains "gta(1)"
"gta" --> the name is reserved, system adds (k), since "gta(1)" is also reserved, systems put k = 2. it becomes "gta(2)"
"avalon" --> not assigned before, remains "avalon"

Example 3:

Input: names = ["onepiece","onepiece(1)","onepiece(2)","onepiece(3)","onepiece"]
Output: ["onepiece","onepiece(1)","onepiece(2)","onepiece(3)","onepiece(4)"]
Explanation: When the last folder is created, the smallest positive valid k is 4, and it becomes "onepiece(4)".

Example 4:

Input: names = ["wano","wano","wano","wano"]
Output: ["wano","wano(1)","wano(2)","wano(3)"]
Explanation: Just increase the value of k each time you create folder "wano".

Example 5:

Input: names = ["kaido","kaido(1)","kaido","kaido(1)"]
Output: ["kaido","kaido(1)","kaido(2)","kaido(1)(1)"]
Explanation: Please note that system adds the suffix (k) to current name even it contained the same suffix before.

Constraints:

• 1 <= names.length <= 5 * 10^4
• 1 <= names[i].length <= 20
• names[i] consists of lower case English letters, digits and/or round brackets.

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给定一个字符串数组，表示每次创建的文件名，如果新的文件名和之前的文件名重名，则需要在后面加上最小的(k)重命名。问最终创建的文件名数组是怎样的。

使用hash表记录每个文件名前缀出现的次数，如果之前没出现，则直接合法；如果之前出现了，则合法的(k)至少是之前出现次数之后的k，枚举找到最小的k。代码如下：

class Solution {
public:
	vector<string> getFolderNames(vector<string>& names) {
		vector<string> ans;
		unordered_map<string, int> show_times;
		for (int i = 0; i < names.size(); ++i) {
			if (show_times.find(names[i]) == show_times.end()) {
				ans.push_back(names[i]);
				show_times[names[i]] = 1;
			}
			else {
				int k = show_times[names[i]];
				string next_name = names[i] + "(" + to_string(k) + ")";
				while (show_times.find(next_name) != show_times.end()) {
					show_times[names[i]] = ++k;
					next_name = names[i] + "(" + to_string(k) + ")";
				}
				ans.push_back(next_name);
				show_times[next_name] = 1;
			}
		}
		return ans;
	}
};

本代码提交AC，用时424MS。