Today I have done leetcode's October LeetCoding Challenge with cpp.

October LeetCoding Challenge 25

Description

Remove Sub-Folders from the Filesystem

Given a list of folders folder, return the folders after removing all sub-folders in those folders. You may return the answer in any order.

If a folder[i] is located within another folder[j], it is called a sub-folder of it. A sub-folder of folder[j] must start with folder[j], followed by a "/". For example, "/a/b" is a sub-folder of "/a", but "/b" is not a sub-folder of "/a/b/c".

The format of a path is one or more concatenated strings of the form: '/' followed by one or more lowercase English letters.

• For example, "/leetcode" and "/leetcode/problems" are valid paths while an empty string and "/" are not.

Example 1:

Input: folder = ["/a","/a/b","/c/d","/c/d/e","/c/f"]
Output: ["/a","/c/d","/c/f"]
Explanation: Folders "/a/b" is a subfolder of "/a" and "/c/d/e" is inside of folder "/c/d" in our filesystem.

Example 2:

Input: folder = ["/a","/a/b/c","/a/b/d"]
Output: ["/a"]
Explanation: Folders "/a/b/c" and "/a/b/d" will be removed because they are subfolders of "/a".

Example 3:

Input: folder = ["/a/b/c","/a/b/ca","/a/b/d"]
Output: ["/a/b/c","/a/b/ca","/a/b/d"]

Constraints:

• 1 <= folder.length <= 4 * 104
• 2 <= folder[i].length <= 100
• folder[i] contains only lowercase letters and '/'.
• folder[i] always starts with the character '/'.
• Each folder name is unique.

Solution

struct TrieNode {
  bool end = false;
  TrieNode *child[128] = {};
};
void insert(TrieNode *root, const string &word) {
  TrieNode *cur = root;
  for(auto c : word) {
    if(!cur->child[c]) {
      cur->child[c] = new TrieNode();
    }
    cur = cur->child[c];
  }
  cur->end = true;
}
bool isSubFolder(TrieNode *root, const string &word) {
  TrieNode *cur = root;
  bool prevFolder = false;
  for(auto c : word) {
    if(prevFolder && c == '/') return true;
    cur = cur->child[c];
    prevFolder = cur->end;
  }
  return false;
}
class Solution {
public:
  vector<string> removeSubfolders(vector<string>& folder) {
    TrieNode *root = new TrieNode();
    for(const auto &folder : folder) {
      insert(root, folder);
    }
    vector<string> answer;
    for(const auto &folder : folder) {
      if(!isSubFolder(root, folder)) answer.push_back(folder);
    }
    return answer;
  }
};