Description Link to heading

1487. Making File Names Unique (Medium)

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 that was 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)".

Constraints:

  • 1 <= names.length <= 5 * 10⁴
  • 1 <= names[i].length <= 20
  • names[i] consists of lowercase English letters, digits, and/or round brackets.

Solution Link to heading

We can use a hash table for processing. unordered_map<string, int> ump, ump[name] shows the occurrences of the string name.

Code Link to heading 

class Solution {
  public:
    vector<string> getFolderNames(vector<string> &names) {
        unordered_map<string, int> ump;
        for (auto &name : names) {
            if (ump.find(name) == ump.end()) {
                ump[name] = 0;
            } else {
                int i = ump[name] + 1;
                while (ump.find(name + "(" + std::to_string(i) + ")") != ump.end()) {
                    ++i;
                }
                ump[name] = i;
                name += "(" + std::to_string(i) + ")";
                ump[name] = 0;
            }
        }
        return names;
    }
};