leetcode 208. realize Trie (Prefix Tree) / trie

 

Implement a Trie (prefix tree), comprising insert, search, and startsWith these three operations.

 

Example:

 

Trie trie = new Trie();

 

trie.insert ( "Apple");
trie.search ( "Apple"); // Returns to true
trie.search ( "App"); // returns to false
trie.startsWith ( "App"); // Returns to true
Trie. INSERT ( "App");
trie.search ( "App"); // returns true
Description:

 

You can assume that all inputs are constituted by the lowercase letters az.
To ensure that all inputs are non-empty string.

 

Source: stay button (LeetCode)
link: https: //leetcode-cn.com/problems/implement-trie-prefix-tree

 

class Trie {
public:
    /** Initialize your data structure here. */
    vector<vector<int>>ch;
    vector<int>val;
    vector<int>a;
    int sz;
    Trie() {
        sz=1;
        for(int i=0;i<26;i++)a.push_back(0);
        ch.push_back(a);
        val.push_back(0);
    }
    int idx(char c){return c-'a';}
    /** Inserts a word into the trie. */
    void insert(string s) {
        int u=0,n=s.length();
        for(int i=0;i<n;i++){
            int c=idx(s[i]);
            if(!ch[u][c]){
                val.push_back(0);
                ch.push_back(a);
                ch[u][c]=sz++;
            }
            u=ch[u][c];
        }
        val[u]=1;
    }
    
    /** Returns if the word is in the trie. */
    bool search(string s) {
        int u=0,n=s.length();
        for(int i=0;i<n;i++){
            int c=idx(s[i]);
            if(!ch[u][c]){
                return false;
            }
            u=ch[u][c];
        }
        if(val[u]==1)return true;
        else return false;
    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    bool startsWith(string s) {
        int u=0,n=s.length();
        for(int i=0;i<n;i++){
            int c=idx(s[i]);
            if(!ch[u][c]){
                return false;
            }
            u=ch[u][c];
        }
        return true;
    }
};

/**
 * Your Trie object will be instantiated and called as such:
 * Trie* obj = new Trie();
 * obj->insert(word);
 * bool param_2 = obj->search(word);
 * bool param_3 = obj->startsWith(prefix);
 */