Leetcode#14 Longest Common Prefix

 1 struct TrieNode {
 2   int count;
 3   map<char, TrieNode *> children;
 4   TrieNode() : count(0) {}
 5 };
 6 
 7 string longestCommonPrefix(vector<string> &strs) {
 8   if (strs.empty()) return "";
 9 
10   TrieNode *root = new TrieNode();
11   root->count = 1;
12   for (auto str : strs) {
13     TrieNode *node = root;
14     for (int i = 0; i < str.length(); i++) {
15       if (node->children.find(str[i]) == node->children.end())
16         node->children.insert(pair<char, TrieNode *>(str[i], new TrieNode()));
17       node = node->children[str[i]];
18       node->count++;
19     }
20   }
21 
22   int len = 0;
23   while (root->children.size() == 1) {
24     root = root->children.begin()->second;
25     if (root->count < strs.size())
26       break;
27     len++;
28   }
29 
30   return strs[0].substr(0, len);
31 }