POJ 1703 Find them, Catch them(种类并查集)

题目链接

这种类型的题目以前见过，今天第一次写，具体过程，还要慢慢理解。

 1 #include <cstring>

 2 #include <cstdio>

 3 #include <string>

 4 #include <iostream>

 5 #include <algorithm>

 6 #include <vector>

 7 using namespace std;

 8 int o[100001];

 9 int flag[100001];

10 int find(int x)

11 {

12     if (x == o[x]) return x;

13     int t = find(o[x]);

14     flag[x] = (flag[o[x]] + flag[x]) % 2;

15     return o[x] = t;

16 }

17 void merge(int x,int y)

18 {

19     int tx,ty;

20     tx = find(x);

21     ty = find(y);

22     if(tx != ty)

23     {

24         o[tx] = ty;

25         flag[tx] = (flag[x]+flag[y]+1)%2;

26     }

27 }

28 int judge(int x,int y)

29 {

30     int tx,ty;

31     tx = find(x);

32     ty = find(y);

33     if(tx != ty)

34     return -1;

35     else

36     return (flag[x] == flag[y]);

37 }

38 int main()

39 {

40     int T,sv,ev,i,n,m;

41     char ch;

42     scanf("%d",&T);

43     while(T--)

44     {

45         scanf("%d%d%*c",&n,&m);

46         for(i = 1;i <= n;i ++)

47         {

48             flag[i] = 0;

49             o[i] = i;

50         }

51         for(i = 0;i < m;i ++)

52         {

53             scanf("%c%*c%d%d%*c",&ch,&sv,&ev);

54             if(ch == 'A')

55             {

56                 int temp = judge(sv,ev);

57                 if(temp == -1)

58                 printf("Not sure yet.\n");

59                 else if(temp == 0)

60                 printf("In different gangs.\n");

61                 else

62                 printf("In the same gang.\n");

63             }

64             else

65             {

66                 merge(sv,ev);

67             }

68         }

69     }

70     return 0;

71 }