并查集 how many tables
2015-10-15 20:20
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How Many Tables
Time Limit : 2000/1000ms (Java/Other) Memory Limit : 65536/32768K (Java/Other)Total Submission(s) : 32 Accepted Submission(s) : 16
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Problem Description
Today is Ignatius' birthday. He invites a lot of friends. Now it's dinner time. Ignatius wants to know how many tables he needs at least. You have to notice that not all the friends know each other, and all the friends do not want to stay withstrangers.
One important rule for this problem is that if I tell you A knows B, and B knows C, that means A, B, C know each other, so they can stay in one table.
For example: If I tell you A knows B, B knows C, and D knows E, so A, B, C can stay in one table, and D, E have to stay in the other one. So Ignatius needs 2 tables at least.
Input
The input starts with an integer T(1<=T<=25) which indicate the number of test cases. Then T test cases follow. Each test case starts with two integers N and M(1<=N,M<=1000). N indicates the number of friends, the friends are marked from1 to N. Then M lines follow. Each line consists of two integers A and B(A!=B), that means friend A and friend B know each other. There will be a blank line between two cases.
Output
For each test case, just output how many tables Ignatius needs at least. Do NOT print any blanks.Sample Input
2 5 3 1 2 2 3 4 5 5 1 2 5
Sample Output
2 4
#include <iostream> const int maxn=1005; int set[maxn]; using namespace std; int set_find(int i)//查找i所在集合代表元素,用路径压缩优化 { if(set[i]<0) return i; else return set[i]=set_find(set[i]); } void join(int a,int b)//将a所在集合并入b所在集合 { a=set_find(a); b=set_find(b); if(a!=b) set[a]=b; } int main() { int t,n,m,x,y; cin>>t; while(t--) { int ant=0; cin>>n>>m; for(int i=0; i<n; i++) set[i]=-1; for(int i=0; i<m; i++) { cin>>x>>y; join(x,y); } for(int i=0; i<n; i++) if(set[i]<0) ant++; cout<<ant<<endl; } return 0; }
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