HDU 1242 Rescue

题目地址：​​点击打开链接​​

思路：从天使搜朋友，得出最短的时间

AC代码：

#include<iostream>
#include<cstring>
using namespace std;
char a[210][210];
int visit[210][210];
int starti,startj,min1,flag;
int x[4] = {-1,1,0,0} ,y[4] = {0,0,-1,1};
void dfs(int i,int j,int len)
{
  int k,m,n;
  if(len > min1)
    return;
  if(a[i][j] == 'r' && len < min1)
  {
    flag = 1;
    min1 = len;
    return;
  }
  if(a[i][j] == 'x')
    len++;
  visit[i][j] = 1;
  for(k=0; k<4; k++)
  {
    m = i + x[k];
    n = j + y[k];
    if(a[m][n] != '#' && !visit[m][n])
    {
      dfs(m,n,len+1);
    }
  }
  visit[i][j] = 0;
}
int main()
{
  int n,m,i,j;
  while(cin>>n>>m)
  {
    flag = 0;
    min1 = 100000000;
    memset(a,'#',sizeof(a));//在外面围一层，省的判断
    memset(visit,0,sizeof(visit));
    for(i=1; i<=n; i++)
    {
      for(j=1; j<=m; j++)
      {
        cin>>a[i][j];
        if(a[i][j] == 'a')
        {
          starti = i;
          startj = j;
        }
      }
    }
    visit[starti][startj] = 1;
    dfs(starti,startj,0);
    if(flag)
      cout<<min1<<endl;
    else
      cout<<"Poor ANGEL has to stay in the prison all his life." <<endl;
  }
  return 0;
}