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43 | class Solution {
public:
int dx[4] = {1, -1, 0, 0};
int dy[4] = {0, 0, 1, -1};
static constexpr int SIZE = 20;
bool vis[SIZE][SIZE] = {0};
bool dfs(int x, int y, int idx, int M, int N,
string& word, vector<vector<char>>& board) {
if (board[x][y] != word[idx])
return false;
if (idx == word.length() - 1)
return true;
for (int i = 0; i < 4; i++) {
if (x + dx[i] >= 0 && x + dx[i] < M &&
y + dy[i] >= 0 && y + dy[i] < N &&
!vis[x + dx[i]][y + dy[i]]) {
vis[x + dx[i]][y + dy[i]] = true;
if (dfs(x + dx[i], y + dy[i], idx + 1, M, N, word, board))
return true;
vis[x + dx[i]][y + dy[i]] = false;
}
}
return false;
}
bool exist(vector<vector<char>>& board, string word) {
int M = board.size();
int N = board[0].size();
for (int i = 0; i < M; i++) {
for (int j = 0; j < N; j++) {
vis[i][j] = true;
if (dfs(i, j, 0, M, N, word, board)) {
return true;
}
vis[i][j] = false;
}
}
return false;
}
};
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