POJ2226 Muddy Fields

最小点覆盖

#include <iostream>
#include <string.h>
using namespace std;
const int size = 700;
char mapp[60][60];
int num1, num2;
int mapp1[size][size], mapp2[size][size];
bool maze[size][size];
const int Go[2][2] = {{0, 1}, {1, 0}};
int n, m;
bool check(int x, int y)
{
     return (x >= 0 && x < n && y >= 0 && y < m);     
}
int xx, yy, st;
void dfs(int sx, int sy, int x[][size], int num)
{
     if (x[sx][sy] != -1)return ;
     x[sx][sy] = num;
     xx = sx + Go[st][0], yy = sy + Go[st][1];
     if (check(xx, yy)){
        dfs(xx, yy, x, num);              
     }    
}
int match[size];
bool visited[size];
bool dfs1(int x, int num)
{
     for (int i = 1; i <= num; i ++){
         if (!maze[x][i] || visited[i])continue;
         visited[i] = true;
         if (match[i] == -1 || dfs1(match[i], num)){
            match[i] = x;
            return true;             
         }
     }
     return false;     
}
int main()
{
    while (scanf("%d%d", &n, &m) != EOF){
          memset(mapp1, 0, sizeof(mapp1));
          memset(mapp2, 0, sizeof(mapp2));
          for (int i = 0; i < n; i ++){
              scanf("%s", mapp[i]);
              for (int j = 0; j < m; j ++){
                  if (mapp[i][j] == '*'){
                     mapp1[i][j] = mapp2[i][j] = -1;               
                  }    
              }    
          }
          st = 0, num1 = 1;
          for (int i = 0; i < n; i ++){
              for (int j = 0; j < m; j ++){
                  if (mapp1[i][j] == -1){
                     dfs(i, j, mapp1, num1);
                     num1 ++;              
                  }
              }    
          }
          st = 1, num2 = 1;
          for (int i = 0; i < m; i ++){
              for (int j = 0; j < n; j ++){
                  if (mapp2[j][i] == -1){
                     dfs(j, i, mapp2, num2); 
                     num2 ++;             
                  }
              }    
          }
          memset(maze, false, sizeof(maze));
          for (int i = 0; i < n; i ++){
              for (int j = 0; j < m; j ++){
                  if (mapp[i][j] == '*'){
                     maze[mapp1[i][j]][mapp2[i][j]] = true;
                  }
              }    
              
          }
          int ans = 0;
          memset(match, -1, sizeof(match));
          for (int i = 1; i <= num1; i ++){
              memset(visited, false, sizeof(visited));
              if (dfs1(i, num2))ans ++;
          }
          printf("%d\n", ans);
    }
    return 0;    
}