Satellite Photographs（dfs）

Satellite Photographs
 Time Limit: 1000MS Memory Limit: 65536K Total Submissions: 6092 Accepted: 2874

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`

Source

dfs即可。

```#include

#include

#include

#include

using namespace std;char mp[1000][82];bool vis[1000][82];int w,h;int sum,maxx;void dfs(int a,int b)   //ab代表坐标{
if(a<0 || a>=h) return;
if(b<0 || b>=w) return;
if(vis[a][b]) return;
if(mp[a][b]=='*')
{
sum++;
vis[a][b]=1;//注意，这是标记的这个点有没有做过起点，所以不用回溯，别混淆
dfs(a-1,b);
dfs(a,b-1);
dfs(a+1,b);
dfs(a,b+1);
}}int main(){
int i,j;
scanf("%d %d",&w,&h);
for(i=0;i

for(j=0;j

maxx=-1;
for(i=0;i

{
for(j=0;j

{
if(vis[i][j]==0)
{
sum=0;
dfs(i,j);
if(maxx

}
}
}
printf("%d",maxx);
return 0;}

```

最新留言

[***.172.111.71]2022年05月22日 08时33分03秒

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