codeforces723 D. Lakes in Berland(并查集)

题目链接：codeforces723 D. Lakes in Berland

参考博客：http://www.cnblogs.com/Geek-xiyang/p/5930245.html

 #include<cstdio>
 #include<cstring>
 #include<vector>
 #include<algorithm>
 #define CLR(a,b) memset((a),(b),sizeof((a)))
 using namespace std;
 const int N = ;
 const int M = ;
 int n, m, k;
 char ch[N][N];
 int val[N][N];
 int fa[M], num[M];
 bool vis[M];
 int dx[] = {,,,-};
 int dy[] = {,-,,};
 void init(){
     CLR(ch,'.');
     int cnt = ;
     for(int i = ; i <= n+; ++i)
         for(int j = ; j <= m+; ++j)
             val[i][j] = ++cnt;
     for(int i = ; i <= cnt; ++i){
         fa[i] = i;
         num[i] = ;
     }
 }
 int fin(int x){
     if(x != fa[x])
         fa[x] = fin(fa[x]);
     return fa[x];
 }
 void uni(int x, int y){
     if((x = fin(x)) == (y = fin(y))) return;
     else {
         fa[x] = y;
         num[y] += num[x];
     }
 }
 void make(int i, int j){
     for(int k = ; k < ; ++k){
         if(ch[dx[k]+i][dy[k]+j] == '.')
             uni(val[i][j], val[dx[k]+i][dy[k]+j]);
     }
 }
 bool cmp(int x, int y){
     return num[x] < num[y];
 }
 vector<int>v;
 int main(){
     int i, j, kk, rt, t;
     scanf("%d%d%d", &n, &m, &k);
     init();
     for(i = ; i <= n+; ++i){
         uni(val[][], val[i][]);
         uni(val[][], val[i][m+]);
     }
     for(i = ; i <= m+; ++i){
         uni(val[][], val[][i]);
         uni(val[][], val[n+][i]);
     }
     for(i = ; i <= n; ++i){
         scanf("%s", ch[i]+);
         ch[i][m+] = '.';//第二遍改时把这句漏了继续WA
     }
     for(i = ; i <= n; ++i)
         for(j =  ; j <= m; ++j)
             if(ch[i][j] == '.')
                 make(i, j);
     for(i = ; i <= n; ++i){
         for(j = ; j <= m; ++j){
             rt = fin(val[i][j]);
             if(ch[i][j] == '.' && fin(val[][]) != rt){
                 if(vis[rt]) continue;
                 else  vis[rt] = true;
                 v.push_back(rt);
             }
         }
     }
     sort(v.begin(), v.end(), cmp);
     int len = v.size();
     t = len;
     int ans = ;
     if(t > k){
         for(i = ; i < len; ++i){
             rt = fin(v[i]);
             if(vis[rt]){
                 vis[rt] = false;
                 t--;
                 for(j = ; j <= n; ++j)
                     for(kk = ; kk <= m; ++kk)//我第一遍把这里写成k导致WA死
                         if(fin(val[j][kk]) == rt) {ch[j][kk] = '*'; ans++;}
             }
             if(t == k) break;
         }
     }
     printf("%d\n", ans);
     for(i = ; i <= n; ++i){
         for(j = ; j <= m; ++j)
             printf("%c", ch[i][j]);
         puts("");
     }
     return ;
 }