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1487. Making File Names Unique.md

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1487. Making File Names Unique

the second one in Weekly Contest 194.

Difficulty : Medium

Related Topics : String、HashTable

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.

Solution

  • mine
    • Java
      • Runtime: 42 ms, faster than 100.00%, Memory Usage: 56 MB, less than 100.00% of Java online submissions 
        // O(N)time O(N)space
public String[] getFolderNames(String[] names) {
    String[] res = new String[names.length];
    Map<String, Integer> recordCount = new HashMap<>();
    for (int i = 0; i < names.length; i++) {
        if (recordCount.containsKey(names[i])) {
            int index = recordCount.get(names[i]) + 1;
            StringBuilder builder = new StringBuilder();
            builder.append(names[i]).append("(").append(index).append(")");
            String t = builder.toString();
            while (recordCount.containsKey(t)) {
                index++;
                builder = new StringBuilder();
                builder.append(names[i]).append("(").append(index).append(")");
                t = builder.toString();
            }
            recordCount.put(names[i], index);
            recordCount.put(t, 0);
            res[i] = t;
        } else {
            recordCount.put(names[i], 0);
            res[i] = names[i];
        }
    }
    return res;
}