Problem I: Satellite Photographs
Time Limit: 1 Sec Memory Limit: 128 MB Submit: 208 Solved: 118 [Submit][Status][Web Board]Description
Farmer John purchased satellite photos of W x H pixels of his farm (1 <= W <= 80, 1 <= H <= 1000) and wishes to determine the largest 'contiguous' (connected) pasture. Pastures are contiguous when any pair of pixels in a pasture can be connected by traversing adjacent vertical or horizontal pixels that are part of the pasture. (It is easy to create pastures with very strange shapes, even circles that surround other circles.)
Each photo has been digitally enhanced to show pasture area as an asterisk ('*') and non-pasture area as a period ('.'). Here is a 10 x 5 sample satellite photo:
..*.....** .**..***** .*...*.... ..****.*** ..****.***
This photo shows three contiguous pastures of 4, 16, and 6 pixels. Help FJ find the largest contiguous pasture in each of his satellite photos.
Input
* Line 1: Two space-separated integers: W and H * Lines 2..H+1: Each line contains W "*" or "." characters representing one raster line of a satellite photograph.
Output
* Line 1: The size of the largest contiguous field in the satellite photo.
Sample Input
10 5
..*.....**
.**..*****
.*...*....
..****.***
..****.***
Sample Output
16
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
char a[1000][1000];
int sum;
void dfs(int x,int y)
{
if(a[x][y]=='*')//注意是单引号//
{
a[x][y]='.';
sum++;
dfs(x,y+1);
dfs(x,y-1);
dfs(x+1,y);
dfs(x-1,y);
}
else if(a[x][y]=='.')
return ;
}
int main()
{
int w,h;
int i,j,k;
int max;
char c;
sum=0;
scanf("%d%d",&w,&h);
for(i=0;i<h;i++)
{
for(j=0;j<w;j++)
{
scanf(" %c",&a[i][j]);//一定要注意空格，因为换行符也是字符//
}
}
max=0;
for(i=0;i<h;i++)
{
for(j=0;j<w;j++)
{
if(a[i][j]=='*')
{
sum=0;//注意初始化sum为0！！！！！！//
dfs(i,j);//从二维数组的第一个*开始搜索//
if(sum>=max)
max=sum;
}
}
}
printf("%d\n",max);
return 0;
}