[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 }
跟着chengyulala刷题之[kuangbin带你飞]之'并查集'专题/斜眼笑
原文地址：https://www.cnblogs.com/pupil-xj/p/11614643.html