hdu 1272 小希的迷宫 (并查集)

 1 #include <map>
 2 #include <queue>
 3 #include <cmath>
 4 #include <vector>
 5 #include <string>
 6 #include <cstdio>
 7 #include <cstring>
 8 #include <climits>
 9 #include <iostream>
10 #include <algorithm>
11 #define INF 0xffffff
12 using namespace std;
13 
14 const int my_max = 100005;
15 int a, b, my_pre[my_max + 2], my_book[my_max + 2];
16 bool my_flag;
17 
18 int my_find(int x)
19 {
20     int n = x;
21     while (n != my_pre[n])
22         n = my_pre[n];
23     int i = x, j;
24     while (my_pre[i] != n)
25     {
26         j = my_pre[i];
27         my_pre[i] = n;
28         i = j;
29     }
30     return n;
31 }
32 
33 void my_join(int aa, int bb)
34 {
35     int n1 = my_find(aa), n2 = my_find(bb);
36     if (n1 != n2) my_pre[n1] = n2;
37     else my_flag = false;
38 }
39 
40 int main()
41 {
42     while (scanf("%d%d", &a, &b), a != -1 || b != -1)
43     {
44         if (a == 0 && b == 0)
45         {
46             printf("Yes\n");
47             continue;
48         }
49         for (int i = 1; i <= my_max; ++ i)
50         {
51             my_pre[i] = i;
52             my_book[i] = 0;
53         }
54         my_book[a] = my_book[b] = 1;
55         my_join(a, b);
56 
57         my_flag = true;
58         while (scanf("%d%d", &a, &b), a || b)
59         {
60             my_join(a, b);
61             my_book[a] = my_book[b] = 1;
62         }
63 
64         int my_cnt = 0;
65         for (int i = 1; i <= my_max; ++ i)
66         {
67             if (my_book[i] && my_pre[i] == i)
68             {
69                 my_cnt ++;
70                 if (my_cnt >= 2)
71                 {
72                     my_flag = false;
73                     break;
74                 }
75             }
76         }
77 
78         if (my_flag)
79             printf("Yes\n");
80         else
81             printf("No\n");
82     }
83     return 0;
84 }