leetcode 日经贴，python code -Word Search II

struct TrieNode {
TrieNode (){
memset(next, 0, sizeof(next));
id = -1;
count = 0;
}
TrieNode* next[26];
int id, count;
};

class Solution {
public:
Solution() {
root = new TrieNode();
}

vector<string> findWords(vector<vector<char>>& board, vector<string>& words) {
vector<string> ans;
int R = board.size();
if (!R) {
return ans;
}
int C = board[0].size();
if (!C) {
return ans;
}
sort(words.begin(), words.end());
int wordslen = words.size();
if (!wordslen) {
return ans;
}
for (int i = 0; i < wordslen; ++i) {
//did't insert the same word twice
if (i == 0 || words[i] != words[i - 1]) {
insert(words[i].c_str(), i);
}
}
vector<vector<bool> > visit(R);
for (int i = 0; i < R; ++i) {
visit[i].resize(C);
}
vector<int> matchids;

for (int i = 0; i < R; ++i) {
for (int j = 0; j < C; ++j) {
match(root, board, visit, R, C, i, j, matchids);
}
}
sort(matchids.begin(), matchids.end());
for (int i = 0; i < matchids.size(); ++i) {
ans.push_back(words[matchids[i]]);
}
return ans;
}

private:
TrieNode* root;
const static int dir[4][2];
void insert(const char* s, int id) {
TrieNode* p = root;
p->count++;
while (*s) {
if (!p->next[*s - 'a']) {
p->next[*s - 'a'] = new TrieNode();
}
p = p->next[*s - 'a'];
p->count++;
++s;
}
p->id = id;
}
int match(TrieNode* cur, vector<vector<char> >& board, vector<vector<bool> >& visit,
int R, int C, int r, int c, vector<int>& matchids) {
if (!cur) {
return 0;
}
int child = board[r][c] - 'a';
if (!cur->next[child]) {
return 0;
}
TrieNode* next = cur->next[child];
int matchcnt = 0;
if (next->id != -1) {
matchids.push_back(next->id);
if (next->count == 1) {
delete next;
cur->next[child] = NULL;
return 1;
} else {
matchcnt++;
next->id = -1;
}
}
visit[r][c] = true;
for (int d = 0; d < 4; ++d) {
int nr = r + dir[d][0];
int nc = c + dir[d][1];
if (nr >= 0 && nr < R && nc >= 0 && nc < C && !visit[nr][nc]) {
matchcnt += match(next, board, visit, R, C, nr, nc, matchids);
}
}
visit[r][c] = false;
if (next->count - matchcnt == 0) {
delete next;
cur->next[child] = NULL;
} else {
next->count -= matchcnt;
}
return matchcnt;
}
};
const int Solution::dir[4][2] = {1, 0, -1, 0, 0, 1, 0, -1};