Zombie in Matrix

Given a 2D grid, each cell is either a wall 2, a zombie 1or people 0 (the number zero, one, two).Zombies can turn the nearest people(up/down/left/right) into zombies every day, but can not through wall. How long will it take to turn all people into zombies? Return -1 if can not turn all people into zombies.

java

class corr {    int x;    int y;    public corr(int x, int y) {        this.x = x;        this.y = y;    }}public class Solution {    /*     * @param grid: a 2D integer grid     * @return: an integer     */    int WALL = 2;    int PEOPLE = 0;    int ZOMBIE = 1;    public int zombie(int[][] grid) {        // write your code here        if (grid == null || grid.length == 0 || grid[0].length == 0) {            return -1;        }        int row = grid.length;        int column = grid[0].length;        Queue<corr> queue = new LinkedList<>();        int people = 0;        int count = 0;        for (int i = 0; i < row; i++) {            for (int j = 0; j < column; j++) {                if (grid[i][j] == PEOPLE) {                    people++;                }                if (grid[i][j] == ZOMBIE) {                    queue.offer(new corr(i, j));                }            }        }        if (people == 0) {            return 0;        }        int[] dir_x = {0, 1, -1, 0};        int[] dir_y = {1, 0, 0, -1};        while (!queue.isEmpty()) {            if (people == 0) {                break;            }            int n = queue.size();            count++;            for (int i = 0; i < n; i++) {                corr node = queue.poll();                for (int j = 0; j < 4; j++) {                    int n_x = node.x + dir_x[j];                    int n_y = node.y + dir_y[j];                    if (isPeople(grid, n_x, n_y)) {                        grid[n_x][n_y] = ZOMBIE;                        people--;                        queue.offer(new corr(n_x, n_y));                    }                }            }        }        if (people != 0) {            return -1;        }        return count;    }    private boolean isPeople(int[][] grid, int x, int y) {        int row = grid.length;        int column = grid[0].length;        return (x >= 0 && x < row && y >= 0 && y < column && grid[x][y] == PEOPLE);    }}

python

from Queue import Queueclass Solution:    """    @param: grid: a 2D integer grid    @return: an integer    """    PEOPLE = 0    ZOMBIE = 1    WALL = 2    def zombie(self, grid):        # write your code here        count, people = 0, 0            queue = Queue()        row, column = len(grid), len(grid[0])        for i in xrange(row):            for j in xrange(column):                if grid[i][j] == self.PEOPLE:                    people += 1                if grid[i][j] == self.ZOMBIE:                    queue.put([i, j])        if people == 0:            return 0        dir_x = [1, 0, 0, -1]        dir_y = [0, -1, 1, 0]        while not queue.empty():            if people == 0:                break            count += 1            n = queue.qsize()            for i in xrange(n):                node = queue.get()                for j in xrange(4):                    n_x = node[0] + dir_x[j]                    n_y = node[1] + dir_y[j]                    if self.isPeople(grid, n_x, n_y):                        grid[n_x][n_y] = self.ZOMBIE                        people -= 1                        queue.put([n_x, n_y])        if people != 0:            return -1        return count            def isPeople(self, grid, x, y):        row, column = len(grid), len(grid[0])        return x >= 0 and x < row and y >= 0 and y < column and grid[x][y] == self.PEOPLE