ACM PKU 1111 Image Perimeters http://acm.pku.edu.cn/JudgeOnline/problem?id=1111

广搜永远记住，下标不要错，COPY时一定要记得改下标:

#include <iostream>
#include <queue>
using namespace std;

char rec[21][21];
bool flag[21][21];

int h[8] = {1,1,1,0,0,-1,-1,-1};    
int s[8] = {1,-1,0,-1,1,0,-1,1};

int row,column,st0,st1;
int sum = 0;

struct node
{
 int r;
 int c;
 node(){};
 node(int x , int y)
 {
  r = x ;
  c = y;
 };
};

queue<node>myqueue;

int temp(int x,int y)
{
 int num = 0;
 if (x == 0 ||rec[x-1][y]== '.')
  num++;
 if (x == row-1 ||rec[x+1][y]== '.')
  num++;
 if (y == 0 ||rec[x][y-1]=='.')
  num++; 
 if (y == column-1 ||rec[x][y+1]=='.')
  num++;
 return num;
}

bool charge (int H,int L)
{
 if( (H >=0) && (H < row) && (L >= 0) && (L < column))
  if ((rec[H][L]=='X') && (flag[H][L] == 0) )
   return true;
  return false;
}

void solve(int H, int L)
{ 
 if (charge(H,L))
 {
  flag[H][L] = 1;
  sum += temp(H,L);
  myqueue.push(node(H , L));
  rec[H][L] = '1';
 }
 while (!myqueue.empty())
 {
  int i ;
  for(i = 0 ;i < 8 ; i++)
  {
   int a = myqueue.front().r;
   int b = myqueue.front().c;
   if(charge(myqueue.front().r  + h[i] ,myqueue.front().c + s[i]))
   {
    myqueue.push(node(myqueue.front().r  + h[i] , myqueue.front().c + s[i]));
    rec[myqueue.front().r  + h[i]][myqueue.front().c + s[i]] = '1';
    sum += temp(myqueue.front().r  + h[i],myqueue.front().c + s[i]);
   }
  }
  myqueue.pop();
 }
} 

int main ()
{
    while (cin>>row>>column>>st0>>st1)
 {
  int i, j;
  memset(flag,0,sizeof (flag));
  sum = 0;
  if (row==0 && column==0 && st0==0 && st1==0 )  break;
  for (i=0; i<row; i++)
   for (j=0; j<column;j++)
    cin >> rec[i][j];
   solve(st0-1,st1-1) ;
   cout<< sum << endl;
 }
 return 0;
}