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
....#.
.....#
......
......
......
......
......
#@...#
.#..#.
11 9
.#.........
.#.#######.
.#.#.....#.
.#.#.###.#.
.#.#..@#.#.
.#.#####.#.
.#.......#.
.#########.
...........
11 6
..#..#..#..
..#..#..#..
..#..#..###
..#..#..#@.
..#..#..#..
..#..#..#..
7 7
..#.#..
..#.#..
###.###
...@...
###.###
..#.#..
..#.#..
0 0
Sample Output
45
59
6
13
59
6
13
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思路:经典搜索,bfs、dfs均可,注意输入房间长宽时,先输入列数再输入行数
Source Program
#include<cstdio> int w,h;//w是列,h是行 int sum; char map[21][21]; int direction[4][2]={{-1,0},{1,0},{0,-1},{0,1}};//方向数组 struct node { int x; int y; }quene[500]; bool judge(int x0,int y0)//判断坐标是否在规定范围内 { if(x0>=0&&x0<h&&y0>=0&&y0<w) return true; else return false; } void bfs(int x0,int y0) { int head,tail; int x,y; int i; head=0,tail=1;//设置队列首尾初值 quene[1].x=x0;quene[1].y=y0;//初始状态存入队列 while(head<tail) { head++;//队首加1,出队 for(i=0;i<4;i++)//依次向上下左右搜索 { x=quene[head].x+direction[i][0]; y=quene[head].y+direction[i][1]; if(map[x][y]=='.'&&judge(x,y))//若子节点符合条件 { map[x][y]='#';//若走过,标记,不能重复走 quene[++tail].x=x;//入队 quene[tail].y=y;//入队 sum++;//走过数+1 } } } } int main() { int x0,y0; int i,j; while(scanf("%d %d",&w,&h)!=EOF)//输入房间长与宽 { getchar(); if(w==0&&h==0) break;//大小为0时终止循环 for(i=0;i<h;i++) { for(j=0;j<w;j++) { scanf("%c",&map[i][j]);//输入每块瓷砖 if(map[i][j]=='@')//记录起始位置 { x0=i; y0=j; } } getchar(); } sum=1; bfs(x0,y0);//搜索 printf("%d\n",sum); } return 0; }