【HDOJ】2473 Junk-Mail Filter

并查集删除结点，方法是构建虚拟点，做映射。

 #include <stdio.h>
 #include <string.h>

 #define MAXNUM 1000050

 int bin[MAXNUM], assist[MAXNUM];
 char visit[MAXNUM];
 int n, ext;

 int find(int x) {
     int r = x;
     int i = x, j;

     while (r != bin[r])
         r = bin[r];

     while (i != r) {
         j = bin[i];
         bin[i] = r;
         i = j;
     }

     return r;
 }

 void merge(int x, int y) {
     int fx, fy;

     fx = find(x);
     fy = find(y);

     if (fx != fy) {
         bin[fx] = fy;
     }
 }

 void extract(int x) {
     bin[ext] = ext;
     assist[x] = ext++;
 }

 int main() {
     int m, t=;
     int i, x, y;
     char ch;

     while (scanf("%d %d", &n, &m)!=EOF && (n||m)) {
         memset(bin, , sizeof(bin));
         memset(assist, , sizeof(assist));
         memset(visit, , sizeof(visit));
         for (i=; i<n; ++i) {
             bin[i] = i;
             assist[i] = i;
         }
         ext = n;
         while (m--) {
             scanf("%*c%c", &ch);
             if (ch == 'M') {
                 scanf("%d %d", &x, &y);
                 x = assist[x];
                 y = assist[y];
                 merge(x, y);
             } else {
                 scanf("%d", &x);
                 extract(x);
             }
         }
         m = ;
         for (i=; i<n; ++i) {
             x = find(assist[i]);
             if (visit[x] == ) {
                 ++m;
                 visit[x] = ;
             }
         }
         printf("Case #%d: %d\n", t++, m);
     }

     return ;
 }