并查集初学（3）无间道之并查集 && POJ2542 && POJ1611

#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <map>
#include <algorithm>

using namespace std;

const int maxn=10005;

int p[maxn];
map<string,int> M;
int m;

int Find(int x)
{
return x == p[x] ? x : p[x]=Find(p[x]);
}
//打标签
int readln()
{
string str;
cin>>str;
if (M.count(str)) return M[str];
else M[str]=++m;
p[m]=m;
return m;
}

int main()
{
int n,relation;
scanf("%d",&n);
m=0;
memset(p,0,sizeof(p));
for (int i=0;i<n;i++)
{
scanf("%d",&relation);
int x=Find(readln());
int y=Find(readln());
if (relation & 1)
{
if (x == y) printf("yes\n");
else printf("no\n");
}
else p[y]=x;
}
return 0;
}

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

const int maxn=50002;

int p[maxn],Rank[maxn];
int ans;

void init(int i)
{
p[i]=i;
Rank[i]=0;
}

int Find(int x)
{
return x != p[x] ? p[x]=Find(p[x]) : x;
}

void union_set(int x,int y)
{
x=Find(x);
y=Find(y);
if (x == y) return;
ans--;//精髓所在
if (Rank[x] > Rank[y])
{
p[y]=x;
}
else
{
p[x]=y;
if (Rank[x] == Rank[y])
Rank[y]++;
}
}

int main()
{
int n,m;
int j=0;
while (scanf("%d%d",&n,&m))
{
if (n == 0 && m == 0) break;
ans=n;
for (int i=1;i<=n;i++)
init(i);
int x,y;
for (int i=0;i<m;i++)
{
scanf("%d%d",&x,&y);
union_set(x,y);
}
printf("Case %d: %d\n",++j,ans);
}
return 0;
}

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

const int maxn = 30001;
int p[maxn],num[maxn],Rank[maxn];

void init(int i)
{
p[i]=i;
num[i]=1;
Rank[i]=0;
}

int Find(int x)
{
return x!=p[x] ? p[x]=Find(p[x]) : x;
}

void union_set(int i,int j)
{
int x=Find(i);
int y=Find(j);
if (x == y) return;
if (Rank[x] > Rank[y])
{
p[y]=x;
num[x]+=num[y];
}
else
{
p[x]=y;
if (Rank[x] == Rank[y])
Rank[y]++;
num[y]+=num[x];
}
}

int main()
{
int n,m;
while (scanf("%d%d",&n,&m))
{
if (n == 0 && m == 0) break;
if (m == 0)
{
printf("1\n");
continue;
}
for (int i=0;i<n;i++)
init(i);
while (m--)
{
int k,x,y;
scanf("%d",&k);
scanf("%d",&x);
for (int i=1;i<k;i++)
{
scanf("%d",&y);
union_set(x,y);
x=y;
}
}
int ans=Find(0);
printf("%d\n",num[ans]);
}
return 0;
}