剑指Offer 12 矩阵中的路径

矩阵中的路径

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个格子开始，每一步可以在矩阵中向左，向右，向上，向下移动一个格子。如果一条路径经过了矩阵中的某一个格子，则之后不能再次进入这个格子。 例如 a b c e s f c s a d e e 这样的3 X 4 矩阵中包含一条字符串"bcced"的路径，但是矩阵中不包含"abcb"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，路径不能再次进入该格子。

# -*- coding:utf-8 -*-
class Solution:
    def __init__(self):
        self.visited = []
        
    def dfs(self,matrix,rows,cols,path,i,j,direction,k):
        if k >= len(path):
            return True
        if i < 0 or i >= rows or j < 0 or j >=cols:
            return False
        if self.visited[i][j] == 1:
            return False
        if matrix[i][j] == path[k]:
            self.visited[i][j] = 1
            for direct in direction:
                x = i + direct[0]
                y = j + direct[1]
                if self.dfs(matrix,rows,cols,path,x,y,direction,k+1):
                    return True
            self.visited[i][j] = 0
        else:
            return False
    
    def hasPath(self, matrix, rows, cols, path):
        array = [[' ' for c in range(cols)]for r in range(rows)]
        idx = 0
        for i in range(rows):
            for j in range(cols):
                cur = matrix[idx]
                idx += 1
                array[i][j] = cur

        direction = [[0,1],[0,-1],[1,0],[-1,0]]
        self.visited = [[0 for c in range(cols)]for r in range(rows)]
        for i in range(rows):
            for j in range(cols):
                if self.dfs(array,rows,cols,path,i,j,direction,0):
                    return True
        return False
        # write code here

 

补充java的实现：

class Solution {
    int[][] visited;

    private boolean dfs(char[][] board, int rows, int cols, String path, int i, int j, int[][] direction, int k) {
        if (k >= path.length()) {
            return true;
        }
        if (i < 0 || i >= rows || j < 0 || j >= cols) {
            return false;
        }
        if (this.visited[i][j] == 1) {
            return false;
        }
        if (board[i][j] == path.charAt(k)) {
            this.visited[i][j] = 1;
            for (int[] direct : direction) {
                int x = i + direct[0];
                int y = j + direct[1];
                if (this.dfs(board, rows, cols, path, x, y, direction, k + 1)) {
                    return true;
                }
            }
            this.visited[i][j] = 0;
        }
        return false;
    }

    public boolean exist(char[][] board, String word) {
        int rows = board.length;
        int cols = board[0].length;

        int[][] direction = new int[][] { { 0, 1 }, { 0, -1 }, { 1, 0 }, { -1, 0 } };
        // System.out.println(direction.length);

        this.visited = new int[rows][cols];

        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                if (this.dfs(board, rows, cols, word, i, j, direction, 0)) {
                    return true;
                }
            }
        }

        return false;
    }
}