hdu 1856 More is better

原题链接：http://acm.hdu.edu.cn/showproblem.php?pid=1856

简单的并查集的运用，如下：

 

 1 #include<cstdio>

 2 #include<cstdlib>

 3 #include<iostream>

 4 #include<algorithm>

 5 const int Max_N = 100050;

 6 struct UnionFind{

 7     int ans, par[Max_N], rank[Max_N], num[Max_N];

 8     inline void init(int n){

 9         ans = 1;

10         for (int i = 1; i < Max_N; i++){

11             par[i] = i;

12             rank[i] = 0;

13             num[i] = 1;

14         }

15     }

16     inline int find(int x){

17         while (x != par[x]){

18             x = par[x] = par[par[x]];

19         }

20         return x;

21     }

22     inline void unite(int x, int y){

23         x = find(x), y = find(y);

24         if (x == y) return;

25         if (rank[x] < rank[y]){

26             par[x] = y;

27             num[y] += num[x];

28             num[x] = 0;

29             ans = std::max(num[y], x);

30         } else {

31             par[y] = x;

32             num[x] += num[y];

33             num[y] = 0;

34             ans = std::max(num[x], ans);

35             if (rank[x] == rank[y]) rank[x]++;

36         }

37     }

38 }rec;

39 int main(){

40 #ifdef LOCAL

41     freopen("in.txt", "r", stdin);

42     freopen("out.txt", "w+", stdout);

43 #endif

44     int n, a, b;

45     while (~scanf("%d", &n)){

46         rec.init(n);

47         for (int i = 0; i < n; i++){

48             scanf("%d %d", &a, &b);

49             rec.unite(a, b);

50         }

51         printf("%d\n", rec.ans);

52     }

53     return 0;

54 }

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