[POJ1703]Find them, Catch them（并查集）

传送门

1.开两个并查集 f[x] 表示 x 的同类 f[x + n] 表示 x 的敌人

——代码

 1 #include <cstdio>
 2 #include <iostream>
 3 #define N 200001
 4
 5 int T, n, m;
 6 int f[N];
 7
 8 inline int read()
 9 {
10     int x = 0, f = 1;
11     char ch = getchar();
12     for(; !isdigit(ch); ch = getchar()) if(ch == ‘-‘) f = -1;
13     for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - ‘0‘;
14     return x * f;
15 }
16
17 inline int find(int x)
18 {
19     return x == f[x] ? x : f[x] = find(f[x]);
20 }
21
22 inline void connect(int x, int y)
23 {
24     x = find(x);
25     y = find(y);
26     f[x] = y;
27 }
28
29 int main()
30 {
31     int i, j, x, y;
32     char s[1];
33     T = read();
34     while(T--)
35     {
36         n = read();
37         m = read();
38         for(i = 1; i <= (n << 1); i++) f[i] = i;
39         for(i = 1; i <= m; i++)
40         {
41             scanf("%s", s);
42             x = read();
43             y = read();
44             if(s[0] == ‘A‘)
45             {
46                 if(find(x) == find(y)) puts("In the same gang.");
47                 else if(find(x) == find(y + n) || find(y) == find(x + n)) puts("In different gangs.");
48                 else puts("Not sure yet.");
49             }
50             else
51             {
52                 connect(x, y + n);
53                 connect(y, x + n);
54             }
55         }
56     }
57 } 

2.带权并查集

——代码

 1 #include <cstdio>
 2 #include <iostream>
 3 #define N 1000001
 4
 5 int T, n, m;
 6 int f[N], d[N];
 7
 8 inline int read()
 9 {
10     int x = 0, f = 1;
11     char ch = getchar();
12     for(; !isdigit(ch); ch = getchar()) if(ch == ‘-‘) f = -1;
13     for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - ‘0‘;
14     return x * f;
15 }
16
17 inline int find(int x)
18 {
19     if(x ^ f[x])
20     {
21         int fx = f[x];
22         f[x] = find(f[x]);
23         d[x] = (d[x] + d[fx]) % 2;
24     }
25     return f[x];
26 }
27
28 inline void connect(int x, int y)
29 {
30     int fx = find(x), fy = find(y);
31     d[fx] = (d[y] + 1 - d[x]) % 2;
32     f[fx] = f[y];
33 }
34
35 int main()
36 {
37     int i, x, y;
38     char s[1];
39     T = read();
40     while(T--)
41     {
42         n = read();
43         m = read();
44         for(i = 1; i <= n; i++) f[i] = i, d[i] = 0;
45         for(i = 1; i <= m; i++)
46         {
47             scanf("%s", s);
48             x = read();
49             y = read();
50             if(s[0] == ‘D‘) connect(x, y);
51             else
52             {
53                 if(find(x) ^ find(y)) puts("Not sure yet.");
54                 else if(d[x] == d[y]) puts("In the same gang.");
55                 else puts("In different gangs.");
56             }
57         }
58     }
59     return 0;
60 }