【HDU2120】Ice_cream's world I（并查集基础题）

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdlib>
 4 #include <cctype>
 5 #include <cmath>
 6 #include <string>
 7 #include <cstdio>
 8 #include <algorithm>
 9 #include <numeric>
10 using namespace std;
11 
12 const int maxnn = 1e4 + 10;
13 int cnt = 0, father[maxnn];
14 
15 int getFather (int x) {
16     if (father[x] != x) {
17         father[x] = getFather (father[x]);
18     }
19     return father[x];
20 }
21 
22 void Union (int p, int q) {
23     int x = getFather (p);
24     int y = getFather (q);
25     if (x != y) {
26         father[y] = x;
27     } else {
28         cnt ++;
29     }
30 }
31 
32 int main () {
33     int n, x;
34     while (cin >> n >> x) {
35         for (int i = 0; i < x; ++ i) {
36             father[i] = i;
37         }
38         cnt = 0;
39         for (int i = 0 ;i < x; ++ i) {
40             int p, q; scanf("%d%d", &p, &q);
41             Union (p, q);
42         }
43 
44 
45         /*for (int i = 0; i < n; ++ i) {
46             if (getFather (i) == i) {
47                 ans ++;
48             }
49         }*/
50         cout << cnt << endl;
51     }
52     return 0;
53 }