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
1 #include<cstdio> 2 #include<cstring> 3 #include<vector> 4 #include<algorithm> 5 #define CLR(a,b) memset((a),(b),sizeof((a))) 6 using namespace std; 7 const int N = 52; 8 const int M = 2800; 9 int n, m, k; 10 char ch[N][N]; 11 int val[N][N]; 12 int fa[M], num[M]; 13 bool vis[M]; 14 int dx[] = {0,0,1,-1}; 15 int dy[] = {1,-1,0,0}; 16 void init(){ 17 CLR(ch,'.'); 18 int cnt = 0; 19 for(int i = 0; i <= n+1; ++i) 20 for(int j = 0; j <= m+1; ++j) 21 val[i][j] = ++cnt; 22 for(int i = 1; i <= cnt; ++i){ 23 fa[i] = i; 24 num[i] = 1; 25 } 26 } 27 int fin(int x){ 28 if(x != fa[x]) 29 fa[x] = fin(fa[x]); 30 return fa[x]; 31 } 32 void uni(int x, int y){ 33 if((x = fin(x)) == (y = fin(y))) return; 34 else { 35 fa[x] = y; 36 num[y] += num[x]; 37 } 38 } 39 void make(int i, int j){ 40 for(int k = 0; k < 4; ++k){ 41 if(ch[dx[k]+i][dy[k]+j] == '.') 42 uni(val[i][j], val[dx[k]+i][dy[k]+j]); 43 } 44 } 45 bool cmp(int x, int y){ 46 return num[x] < num[y]; 47 } 48 vector<int>v; 49 int main(){ 50 int i, j, kk, rt, t; 51 scanf("%d%d%d", &n, &m, &k); 52 init(); 53 for(i = 0; i <= n+1; ++i){ 54 uni(val[0][0], val[i][0]); 55 uni(val[0][0], val[i][m+1]); 56 } 57 for(i = 0; i <= m+1; ++i){ 58 uni(val[0][0], val[0][i]); 59 uni(val[0][0], val[n+1][i]); 60 } 61 for(i = 1; i <= n; ++i){ 62 scanf("%s", ch[i]+1); 63 ch[i][m+1] = '.';//第二遍改时把这句漏了继续WA 64 } 65 for(i = 1; i <= n; ++i) 66 for(j = 1 ; j <= m; ++j) 67 if(ch[i][j] == '.') 68 make(i, j); 69 for(i = 1; i <= n; ++i){ 70 for(j = 1; j <= m; ++j){ 71 rt = fin(val[i][j]); 72 if(ch[i][j] == '.' && fin(val[0][0]) != rt){ 73 if(vis[rt]) continue; 74 else vis[rt] = true; 75 v.push_back(rt); 76 } 77 } 78 } 79 sort(v.begin(), v.end(), cmp); 80 int len = v.size(); 81 t = len; 82 int ans = 0; 83 if(t > k){ 84 for(i = 0; i < len; ++i){ 85 rt = fin(v[i]); 86 if(vis[rt]){ 87 vis[rt] = false; 88 t--; 89 for(j = 1; j <= n; ++j) 90 for(kk = 1; kk <= m; ++kk)//我第一遍把这里写成k导致WA死 91 if(fin(val[j][kk]) == rt) {ch[j][kk] = '*'; ans++;} 92 } 93 if(t == k) break; 94 } 95 } 96 printf("%d\n", ans); 97 for(i = 1; i <= n; ++i){ 98 for(j = 1; j <= m; ++j) 99 printf("%c", ch[i][j]); 100 puts(""); 101 } 102 return 0; 103 }
