LeetCode14. Longest Common Prefix(字典树：最长公共前缀)

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题目链接：https://leetcode.com/problems/longest-common-prefix/

Write a function to find the longest common prefix string amongst an array of strings.（最长公共前缀）

解题思路：字典树。以任一串去查找，找到最长的且匹配数为n的即可，水题。

struct Trie{    Trie *next[26];    int cnt;    //string str;}*root;int n;string ans;void insert(string s){    Trie *p = root,*pnew;    for(int i = 0;i < s.size();++ i){        int x = s[i] - 'a';        if(p->next[x] == NULL){          pnew = new Trie;          pnew->cnt = 1;          for(int j = 0;j < 26;++ j){              pnew->next[j] = NULL;          }          p->next[x] = pnew;        }        else p->next[x]->cnt++;        p=p->next[x];    }}int search(string s){    Trie *p = root;    bool f = 0;    for(int i = 0;i < s.size();++ i){        int x = s[i] - 'a';        if(p->next[x] == NULL) return 0;        if(p->next[x]->cnt == n){            ans = s.substr(0,i+1);            f = 1;        }        p = p->next[x];    }    return f;}void init(){    root = new Trie;    root->cnt = 0;    for(int i = 0;i < 26;++ i){        root->next[i] = NULL;    }}class Solution {public:    string longestCommonPrefix(vector<string>& strs) {      n = strs.size();      if(!n) return ans = "";      init();      for(int i = 0;i < n;++ i){          insert(strs[i]);      }      if(!search(strs[0])) return ans = "";      return ans;    }};

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