纪念一下刷的第100道水题
纪念一下本辣鸡在hdu刷的第100道水题,
比较标准的dfs..
Red and Black
Problem Description
There is a rectangular room, covered with square tiles. Each tile is colored either red or black. A man is standing on a black tile. From a tile, he can move to one of four adjacent tiles. But he can’t move on red tiles, he can move only on black tiles.
Write a program to count the number of black tiles which he can reach by repeating the moves described above.
Input
The input consists of multiple data sets. A data set starts with a line containing two positive integers W and H; W and H are the numbers of tiles in the x- and y- directions, respectively. W and H are not more than 20.
There are H more lines in the data set, each of which includes W characters. Each character represents the color of a tile as follows.
‘.’ – a black tile
‘#’ – a red tile
‘@’ – a man on a black tile(appears exactly once in a data set)
Output
For each data set, your program should output a line which contains the number of tiles he can reach from the initial tile (including itself).
Sample Input
6 9
….#.
…..#
……
……
……
……
……
#@…#
.#..#.
11 9
.#………
.#.#######.
.#.#…..#.
.#.#.###.#.
.#.#..@#.#.
.#.#####.#.
.#…….#.
.#########.
………..
11 6
..#..#..#..
..#..#..#..
..#..#..###
..#..#..#@.
..#..#..#..
..#..#..#..
7 7
..#.#..
..#.#..
###.###
…@…
###.###
..#.#..
..#.#..
0 0
Sample Output
45
59
6
13
代码实现
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import java.util.Scanner; public class Dfs1312 { public static char a[][]; public static int book[][]; public static int l; public static int h; public static int sum; public static void main(String[] args) { // TODO Auto-generated method stub Scanner in = new Scanner(System.in); while (in.hasNext()) { l = in.nextInt(); h = in.nextInt(); if (h == 0 && l == 0) { break; } a = new char[h][l]; int startx = 0; int starty = 0; book = new int[h][l];// 没走的记录为0 for (int i = 0; i < h; i++) { String str = in.next(); in.nextLine(); a[i] = str.toCharArray(); for (int j = 0; j < l; j++) { if (a[i][j] == '@') {// 记录出发点 startx = i; starty = j; } } } book[startx][starty] = 1;// 标记出发点已走 sum = 1; dfs(startx, starty); System.out.println(sum); } } static void dfs(int x, int y) { int[][] next = { { 0, 1 }, { 1, 0 }, { 0, -1 }, { -1, 0 } }; int tx, ty; for (int i = 0; i < 4; i++) {// 计算下一点坐标 tx = x + next[i][0]; ty = y + next[i][1]; // 判断是否越界 if (tx < 0 || tx >= h || ty < 0 || ty >= l) { continue; } if ((a[tx][ty] == '.' || a[tx][ty] == '@') && book[tx][ty] == 0) {// 可以往下走 book[tx][ty] = 1;// 标记已走 sum++; // System.out.println(tx+" "+ty); // for(int k=0;k<h;k++){ // for(int j=0;j<l;j++){ // System.out.print(book[k][j]); // } // System.out.println(); // } dfs(tx, ty); } } } } |
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