跟着chengyulala刷题之[kuangbin带你飞]之'并查集'专题/斜眼笑

Posted 2022-12-08 pupil-xj

[kuangbin带你飞] 专题1-23 https://vjudge.net/article/187

 

专题五 并查集 
POJ 2236 Wireless Network  http://poj.org/problem?id=2236
POJ 1611 The Suspects  http://poj.org/problem?id=1611
HDU 1213 How Many Tables  http://acm.hdu.edu.cn/showproblem.php?pid=1213
HDU 3038 How Many Answers Are Wrong  http://acm.hdu.edu.cn/showproblem.php?pid=3038
POJ 1182 食物链  https://vjudge.net/problem/POJ-1182
POJ 1417 True Liars  https://vjudge.net/problem/POJ-1417
POJ 1456 Supermarket  http://poj.org/problem?id=1456
POJ 1733 Parity game  http://poj.org/problem?id=1733
POJ 1984 Navigation Nightmare  https://vjudge.net/problem/POJ-1984
POJ 2492 A Bug‘s Life  https://vjudge.net/problem/POJ-2492
POJ 2912 Rochambeau  https://vjudge.net/problem/POJ-2912
ZOJ 3261 Connections in Galaxy War  https://vjudge.net/problem/ZOJ-3261
HDU 1272 小希的迷宫  http://acm.hdu.edu.cn/showproblem.php?pid=1272
POJ 1308 Is It A Tree?  http://poj.org/problem?id=1308

 

// hdu 1272 & poj 1308

// "求树是否是个环" ,水。

 1 #include<cstdio>
 2 #include<cstring>
 3 using namespace std;
 4 
 5 const int MAXN = 1e3+5;
 6 
 7 inline int read() 
 8     char c = getchar(); int s = 0, f = 1;
 9     while(c < ‘0‘ || c > ‘9‘)  if(c == ‘-‘) f = -1; c = getchar(); 
10     while(c >= ‘0‘ && c <= ‘9‘)  s = s*10 + c-‘0‘, c = getchar();
11     return s*f;
12 
13 
14 int p[MAXN];
15 
16 inline int find(int x)  return p[x] == x ? x : p[x] = find(p[x]); 
17 
18 int main() 
19     int s, e;
20     int T = 1;
21     while(1) 
22         bool flag = true;
23         while(1)  //scanf("%d%d", &s, &e) == 2 && s
24             s = read(), e = read();
25             if(s == 0 && e == 0) break;
26             if(s == -1) return 0;
27             if(!p[s]) p[s] = s;
28             if(!p[e]) p[e] = e;
29             int x = find(s);
30             int y = find(e);
31             if(x == y) flag = false;
32             else p[x] = y;
33         
34         int ans = 0;
35         for(int i = 1; i <= MAXN; ++i) 
36             if(p[i] == i) ans++;
37             p[i] = 0;
38         
39 
40         printf("Case %d is ", T++);
41         if(!flag || ans > 1) printf("not a tree.\n");
42         else printf("a tree.\n");
43     
44     return 0;
45