并查集基础题,没什么好理解的,纯粹是因为学kruskal而学的并查集
code:
/* ID: yueqiq PROG: numtri LANG: C++ */ #include <set> #include <map> #include <ctime> #include <queue> #include <cmath> #include <stack> #include <limits> #include <vector> #include <bitset> #include <string> #include <cstdio> #include <cstring> #include <fstream> #include <string.h> #include <iostream> #include <algorithm> #define Si set<int> #define LL long long #define pb push_back #define PS printf(" ") #define Vi vector<int> #define LN printf("\n") #define lson l,m,rt << 1 #define rson m+1,r,rt<<1|1 #define SD(a) scanf("%d",&a) #define PD(a) printf("%d",a) #define SET(a,b) memset(a,b,sizeof(a)) #define FF(i,a) for(int i(0);i<(a);i++) #define FD(i,a) for(int i(a);i>=(1);i--) #define FOR(i,a,b) for(int i(a);i<=(b);i++) #define FOD(i,a,b) for(int i(a);i>=(b);i--) #define readf freopen("input.txt","r",stdin) #define writef freopen("output.txt","w",stdout) const int maxn = 30001; const int INF = 0x3fffffff; const int dx[]={0,1,0,-1}; const int dy[]={1,0,-1,0}; const double pi = acos(-1.0); using namespace std; int N,M; int num[maxn],pre[maxn]; void Make_Set(int k){ num[k]=1; pre[k]=k; } int Find_Set(int k){ if(k!=pre[k]){ pre[k]=Find_Set(pre[k]);//回溯赋值,压缩路径 } return pre[k]; } //union the set of x,y void Union_Set(int x,int y){ x=Find_Set(x); y=Find_Set(y); if(x==y) return; if(num[x]>=num[y]){ pre[y]=x; num[x]+=num[y]; }else{ pre[x]=y; num[y]+=num[x]; } } int main() { while(~scanf("%d%d",&N,&M) && (N||M)){ FF(i,N) Make_Set(i); int t,a,b; FF(i,M){ SD(t);SD(a); FOR(i,2,t){ SD(b); Union_Set(a,b); } } // FF(i,N){ // if(i!=pre[i]){ // printf("the s:%d pre:%d num:%d\n",i,pre[i],num[Find_Set(i)]); // } // } PD(num[Find_Set(0)]);LN; } return 0; }