懒人读算法(十一)-找文字

趣味题:

给一个字母矩阵，在给你一串字母，你要在字母矩阵里找到，且字母要上下左右相邻，且每个字母只能用一次
如:字母矩阵如下:

// [//   ['A','B','C','E'],//   ['S','F','C','S'],//   ['A','D','E','E']// ]

当输入 word = “ABCCED”, -> returns true,
当输入 word = “SEE”, -> returns true,
当输入 word = “ABCB”, -> returns false.

答案:

public class Solution {    public boolean exist(char[][] board, String word) {        char[] w = word.toCharArray();        for(int i = 0; i < board.length; i++) {            for(int j = 0; j < board[0].length; j++) {                if(search(board, i, j, w, 0)) return true;            }        }        return false;    }    public boolean search(char[][] board, int i, int j, char[] w, int index) {        if(index == w.length) return true;        if(i < 0 || i >= board.length || j < 0 || j >= board[0].length) return false;        if(board[i][j] != w[index]) return false;        board[i][j] ^= 256;        boolean exist = search(board, i + 1, j, w, index + 1) ||                        search(board, i - 1, j, w, index + 1) ||                        search(board, i, j + 1, w, index + 1) ||                        search(board, i, j - 1, w, index + 1);        board[i][j] ^= 256;        return exist;    }}