# Description

Given a 2D board and a list of words from the dictionary, find all words in the board.

Each word must be constructed from letters of sequentially adjacent cell, where “adjacent” cells are those horizontally or vertically neighboring. The same letter cell may not be used more than once in a word.

For example,
Given words = [“oath”,”pea”,”eat”,”rain”] and board =

``````[
['o','a','a','n'],
['e','t','a','e'],
['i','h','k','r'],
['i','f','l','v']
]
``````

Return [“eat”,”oath”].

The original problem is here.

The original code is here.

# My Solution

I solve this problem in C++, as below:

``````/*
*Word Search II
*Author: shuaijiang
*Email: zhaoshuaijiang8@gmail.com
*/
#include<iostream>
#include<vector>
using namespace std;

class TrieNode{
public:
bool iskey;
TrieNode * childern[26];
TrieNode(){
iskey = false;
for(int i=0;i<26;++i){
childern[i] = NULL;
}
}
};
class Solution {
public:
vector<string> res;
int row;
int col;
vector<string> findWords(vector<vector<char>>& board, vector<string>& words) {
root = new TrieNode();

int wordNum = words.size();
if(wordNum <= 0)
return res;

row = board.size();
col = board[0].size();

//create tried tree
for(int i=0;i<wordNum;++i){
string word = words[i];
int wordLen = word.size();
TrieNode * node = root;
char ch;
for(int j=0;j<wordLen;++j){
ch = word[j];

if(node->childern[ch - 'a'] == NULL){
node->childern[ch - 'a'] = new TrieNode() ;
}
if(j == wordLen-1){
node->childern[ch - 'a']->iskey = true;
}
node =  node->childern[ch-'a'];

}
}
// find the words in the board

for(int i=0;i<row;i++){
for(int j=0;j<col;j++){
vector<vector<bool>> path(row, vector<bool>(col, false));
char ch = board[i][j];
if(root->childern[ch-'a'] != NULL)
find(board, path, i, j, root, "");
}
}
return res;
}
void find(vector<vector<char>>& board, vector<vector<bool>> &path, int i, int j, TrieNode *node, string str){
if(i<0 || i>=row || j< 0 || j>=col)
return;
if(path[i][j])
return ;
char ch = board[i][j];
node = node->childern[ch-'a'];
if(node == NULL)
return;

str.push_back(ch);
if(node->iskey){
res.push_back(str);
node->iskey = false;
}

path[i][j] = true;
if(i-1>=0 && i-1<row)
find(board, path, i-1, j, node, str);
if(i+1>=0 && i+1<row)
find(board, path, i+1, j, node, str);
if(j-1>=0 && j-1<col)
find(board, path, i, j-1, node, str);
if(j+1>=0 && j+1<col)
find(board, path, i, j+1, node, str);

path[i][j] = false;    //should be set to false
}
private:
TrieNode * root;
};

int main(){
Solution s;
vector<vector<char>> board(1,vector<char>(2,'a'));
vector<string> words(1,"a");
vector<string> res = s.findWords(board, words);
cout<<"res.size"<<res.size();
/*
for(int i=0;i<res.size();++i){
cout<<res[i]<<endl;
}*/
return 0;

}
``````