//学习大佬的,dfs + 剪枝
class Solution {
public boolean exist(char[][] board, String word) {
char[] words = word.toCharArray();
for(int i = 0;i < board.length;i++){
for(int j = 0;j < board[0].length;j++){
if(dfs(board,words,i,j,0)){
return true;
}
}
}
return false;
}
public boolean dfs(char[][] board,char[] word,int i,int j,int index){
if(i < 0 || i >= board.length || j < 0 || j >= board[0].length
|| word[index] != board[i][j]){
return false;
}
if(index == word.length - 1){
return true;
}
board[i][j] = ' ';
boolean res = dfs(board,word,i+1,j,index+1) || dfs(board,word,i-1,j,index+1) ||
dfs(board,word,i,j+1,index+1) || dfs(board,word,i,j-1,index+1);
board[i][j] = word[index];
return res;
}
}