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【HDOJ】2473 Junk-Mail Filter
并查集删除结点,方法是构建虚拟点,做映射。
1 #include <stdio.h> 2 #include <string.h> 3 4 #define MAXNUM 1000050 5 6 int bin[MAXNUM], assist[MAXNUM]; 7 char visit[MAXNUM]; 8 int n, ext; 9 10 int find(int x) { 11 int r = x; 12 int i = x, j; 13 14 while (r != bin[r]) 15 r = bin[r]; 16 17 while (i != r) { 18 j = bin[i]; 19 bin[i] = r; 20 i = j; 21 } 22 23 return r; 24 } 25 26 void merge(int x, int y) { 27 int fx, fy; 28 29 fx = find(x); 30 fy = find(y); 31 32 if (fx != fy) { 33 bin[fx] = fy; 34 } 35 } 36 37 void extract(int x) { 38 bin[ext] = ext; 39 assist[x] = ext++; 40 } 41 42 int main() { 43 int m, t=1; 44 int i, x, y; 45 char ch; 46 47 while (scanf("%d %d", &n, &m)!=EOF && (n||m)) { 48 memset(bin, 0, sizeof(bin)); 49 memset(assist, 0, sizeof(assist)); 50 memset(visit, 0, sizeof(visit)); 51 for (i=0; i<n; ++i) { 52 bin[i] = i; 53 assist[i] = i; 54 } 55 ext = n; 56 while (m--) { 57 scanf("%*c%c", &ch); 58 if (ch == ‘M‘) { 59 scanf("%d %d", &x, &y); 60 x = assist[x]; 61 y = assist[y]; 62 merge(x, y); 63 } else { 64 scanf("%d", &x); 65 extract(x); 66 } 67 } 68 m = 0; 69 for (i=0; i<n; ++i) { 70 x = find(assist[i]); 71 if (visit[x] == 0) { 72 ++m; 73 visit[x] = 1; 74 } 75 } 76 printf("Case #%d: %d\n", t++, m); 77 } 78 79 return 0; 80 }
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