How Many Islands?--SOJ 2013week2.1001

Description

You are given a marine area map that is a mesh of squares, each representing either a land or sea area. Figure B-1 is an example of a map.



You can walk from a square land area to another if they are horizontally, vertically, or diagonally adjacent to each other on the map. Two areas are on the same island if and only if you can walk from one to the other possibly through other land areas. The
marine area on the map is surrounded by the sea and therefore you cannot go outside of the area on foot.

You are requested to write a program that reads the map and counts the number of islands on it. For instance, the map in Figure B-1 includes three islands.

Input

The input consists of a series of datasets, each being in the following format.

w h

c1,1 c1,2 ... c1,w
c2,1 c2,2 ... c2,w

...
ch,1 ch,2 ... ch,w

w and h are positive integers no more than 50 that represent the width and the height of the given map, respectively. In other words, the map consists of w×h squares
of the same size. w and h are separated by a single space.

ci, j is either 0 or 1 and delimited by a single space. If ci, j = 0, the square that is the i-th
from the left and j-th from the top on the map represents a sea area. Otherwise, that is, if ci, j = 1, it represents a land area.

The end of the input is indicated by a line containing two zeros separated by a single space.

Output

For each dataset, output the number of the islands in a line. No extra characters should occur in the output.

Sample Input
 Copy sample input to clipboard

1 1
0
2 2
0 1
1 0
3 2
1 1 1
1 1 1
5 4
1 0 1 0 0
1 0 0 0 0
1 0 1 0 1
1 0 0 1 0
5 4
1 1 1 0 1
1 0 1 0 1
1 0 1 0 1
1 0 1 1 1
5 5
1 0 1 0 1
0 0 0 0 0
1 0 1 0 1
0 0 0 0 0
1 0 1 0 1
0 0

Sample Output

0
1
1
3
1
9// Problem#: 7675
// Submission#: 1966541
// The source code is licensed under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License
// URI: http://creativecommons.org/licenses/by-nc-sa/3.0/ // All Copyright reserved by Informatic Lab of Sun Yat-sen University
/*
可以走水平 垂直
*/
#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
using namespace std;
bool map[58][58];
bool vis[58][58];
int heng[]={-1,-1,-1,0,0,1,1,1};
int zong[]={-1,0,1,-1,1,-1,0,1};
int w,h;//w是列m,h是行
int sum;
void dfs(int r,int c)
{
vis[r][c]=1;
for(int i=0;i<8;i++)
{
int rr=r+heng[i];
int cc=c+zong[i];
if((rr>=1&&rr<=h)&&(cc>=1&&cc<=w))
{
if(!vis[rr][cc]&&map[rr][cc])
{
dfs(rr,cc);
}
}
}
}
int main()
{
while(scanf("%d%d",&w,&h)==2&&(w||h))
{
int a;
sum=0;
memset(vis,0,sizeof(vis));
for(int i=1;i<=h;i++)
{
for(int j=1;j<=w;j++)
{
cin>>a;
map[i][j]=a;
}
}
for(int i=1;i<=h;i++)
{
for(int j=1;j<=w;j++)
{
if(map[i][j]&&!vis[i][j])
{
sum++;
dfs(i,j);
}
}
}
cout<<sum<<endl;
}
return 0;
}