poj1703 Find them, Catch them

思路：

关系型并查集。简化的食物链。

实现：

 1 #include <iostream>
 2 #include <cstdio>
 3 using namespace std;
 4 
 5 const int MAXN = 100000;
 6 
 7 int a[MAXN + 10];
 8 int par[2 * MAXN + 10];
 9 int ran[2 * MAXN + 10];
10 int t, n, m, x, y;
11 char p;
12 
13 void init(int n)
14 {
15     for (int i = 0; i <= n; i++)
16     {
17         par[i] = i;
18         ran[i] = 0;
19     }
20 }
21 
22 int find(int x)
23 {
24     if (x == par[x])
25         return x;
26     return par[x] = find(par[x]);
27 }
28 
29 void unite(int x, int y)
30 {
31     x = find(x);
32     y = find(y);
33     if (x == y)
34     {
35         return;
36     }
37     if (ran[x] < ran[y])
38     {
39         par[x] = y;
40     }
41     else
42     {
43         par[y] = x;
44         if (ran[x] == ran[y])
45         {
46             ran[x] ++;
47         }
48     }
49 }
50 
51 bool same(int x, int y)
52 {
53     return find(x) == find(y);
54 }
55 
56 int main()
57 {
58     cin >> t;
59     while (t--)
60     {
61         cin >> n >> m;
62         getchar();
63         init(2 * n);
64         for (int i = 0; i < m; i++)
65         {
66             scanf("%c %d %d", &p, &x, &y);
67             getchar();
68             x--;
69             y--;
70             if (p == 'D')
71             {
72                 unite(x, y + n);
73                 unite(x + n, y);
74             }
75             else
76             {
77                 if (same(x, y) || same(x + n, y + n))
78                 {
79                     puts("In the same gang.");
80                 }
81                 else if (same(x + n, y) || same(x, y + n))
82                 {
83                     puts("In different gangs.");
84                 }
85                 else
86                 {
87                     puts("Not sure yet.");
88                 }
89             }
90         }
91     }
92     return 0;
93 }