题目描述

请设计一个函数，用来判断在一个矩阵中是否存在一条包含某字符串所有字符的路径。路径可以从矩阵中的任意一格开始，每一步可以在矩阵中向左、右、上、下移动一格。如果一条路径经过了矩阵的某一格，那么该路径不能再次进入该格子。例如，在下面的3×4的矩阵中包含一条字符串“bfce”的路径（路径中的字母用加粗标出）。

[["a","b","c","e"],
["s","f","c","s"],
["a","d","e","e"]]

但矩阵中不包含字符串“abfb”的路径，因为字符串的第一个字符b占据了矩阵中的第一行第二个格子之后，路径不能再次进入这个格子。

示例 1：

输入：board = [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], word = "ABCCED"
输出：true
示例 2：

输入：board = [["a","b"],["c","d"]], word = "abcd"
输出：false
提示：

1 <= board.length <= 200
1 <= board[i].length <= 200

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/ju-zhen-zhong-de-lu-jing-lcof

解题思路

本题涉及到路径问题，可采用深度优先搜索算法。依次从每个点开始进行深度搜索，若搜索成功则返回true，否则继续下个点的搜索。

代码

bool dfs(char** board, int boardSize, int* boardColSize, char* word, int row, int col, int length)
{
    if((row < 0) || (row >= boardSize) || (col < 0) || (col >= *boardColSize) || (board[row][col] != word[length]))
    {
        return false;
    }

    if(length == strlen(word) - 1)
    {
        return true;
    }

    char temp = board[row][col];
    board[row][col] = '*';
    bool res = dfs(board, boardSize, boardColSize, word, row, col + 1, length + 1) || dfs(board, boardSize, boardColSize, word, row, col - 1, length + 1) || dfs(board, boardSize, boardColSize, word, row + 1, col, length + 1) || dfs(board, boardSize, boardColSize, word, row - 1, col, length + 1);

    board[row][col] = temp;

    return res;
}

bool exist(char** board, int boardSize, int* boardColSize, char* word){
    for (int i = 0; i < boardSize; i++)
    {
        for (int j = 0; j < *boardColSize; j++)
        {
            if(dfs(board, boardSize, boardColSize, word, i, j, 0))
                return true;
        }
    }

    return false;
}

执行结果