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| class Solution {
private static final int[][] DIRECTIONS = new int[][]{{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
public boolean exist(char[][] board, String word) {
int m = board.length, n = board[0].length;
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
if (dfs(board, i, j, word, 0)) {
return true;
}
}
}
return false;
}
private boolean dfs(char[][] board, int i, int j, String word, int index) {
int m = board.length, n = board[0].length;
if (index == word.length() - 1) {
if (board[i][j] == word.charAt(index)) {
return true;
} else {
return false;
}
}
if (board[i][j] == word.charAt(index)) {
char c = board[i][j];
board[i][j] = '*';
for (int[] direction : DIRECTIONS) {
int nextI = i + direction[0], nextJ = j + direction[1];
if (nextI >= 0 && nextI < m && nextJ >= 0 && nextJ < n) {
if (dfs(board, nextI, nextJ, word, index + 1)) {
return true;
}
}
}
board[i][j] = c;
}
return false;
}
}
|