hihocoder offer收割编程练习赛11 C 岛屿3

思路：

并查集的应用。

实现：

 #include <iostream>
 #include <cstdio>
 using namespace std;
 
 bool a[][];
 int n, x, y;
 int par[];
 int ran[];
 int dx[] = { , , -,  };
 int dy[] = { , , , - };
 
 void init(int n)
 {
     for (int i = ; i < n; i++)
     {
         ran[i] = ;
         par[i] = i;
     }
 }
 
 int find(int x)
 {
     if (par[x] == x)
         return x;
     return par[x] = find(par[x]);
 }
 
 void unite(int x, int y)
 {
     x = find(x);
     y = find(y);
     if (x == y)
         return;
     if (ran[x] < ran[y])
         par[x] = y;
     else
     {
         par[y] = x;
         if (ran[x] == ran[y])
             ran[x]++;
     }
 }
 
 bool same(int x, int y)
 {
     return find(x) == find(y);
 }
 
 int trans(int x, int y)
 {
     return x *  + y;
 }
 
 int main()
 {
     init();
     cin >> n;
     int now = , c = ;
     for (int i = ; i < n; i++)
     {
         now++;
         c += ;
         cin >> x >> y;
         a[x][y] = true;
         int tmp = trans(x, y);
         for (int j = ; j < ; j++)
         {
             int nx = x + dx[j];
             int ny = y + dy[j];
             if (nx >=  && nx <  && ny >=  && ny <  && a[nx][ny])
             {
                 int t = trans(nx, ny);
                 if (!same(tmp, t))
                 {
                     unite(tmp, t);
                     now--;
                 }
                 c -= ;
             }
         }
         cout << now << " " << i +  << " " << c << endl;
     }
     return ;
 }