hdu1856 并查集

题目链接：http://icpc.njust.edu.cn/Problem/Hdu/1856/

题目就是要求并查集中各树的大小的最大值，我们只要在根节点处存树的大小就可以，合并也是合并根节点的数，最后扫一遍即可。

代码如下：

 #include<bits/stdc++.h>
 using namespace std;
 typedef unsigned int ui;
 typedef long long ll;
 typedef unsigned long long ull;
 #define pf printf
 #define mem(a,b) memset(a,b,sizeof(a))
 #define prime1 1e9+7
 #define prime2 1e9+9
 #define pi 3.14159265
 #define lson l,mid,rt<<1
 #define rson mid+1,r,rt<<1|1
 #define scand(x) scanf("%llf",&x)
 #define f(i,a,b) for(int i=a;i<=b;i++)
 #define scan(a) scanf("%d",&a)
 #define mp(a,b) make_pair((a),(b))
 #define P pair<int,int>
 #define dbg(args) cout<<#args<<":"<<args<<endl;
 #define inf 0x3f3f3f3f
 const int maxn=1e7+;
 int n,m,t;
 inline int read(){
     int ans=,w=;
     char ch=getchar();
     while(!isdigit(ch)){if(ch=='-')w=-;ch=getchar();}
     while(isdigit(ch))ans=(ans<<)+(ans<<)+ch-'',ch=getchar();
     return ans*w;
 }
 int f[maxn],cnt[maxn],ans=;
 void init()
 {
     f(i,,maxn-)f[i]=i;
     f(i,,maxn-)cnt[i]=;
     ans=;
 }
 int find(int x)
 {
     if(x==f[x])return x;
     return f[x]=find(f[x]);
 }
 void Union(int x,int y)
 {
     int fx=find(x);
     int fy=find(y);
     if(fx==fy)return ;
     else
     {
         f[fx]=fy;
         cnt[fy]+=cnt[fx];
     }
 }
 int main()
 {
     //freopen("input.txt","r",stdin);
     //freopen("output.txt","w",stdout);
     std::ios::sync_with_stdio(false);
     while(scan(m)!=EOF)
     {
         int a,b;
         init();
         if(m==)
         {
             pf("1\n");
             continue;
         }
         int maxr=;
         f(i,,m)
         {
             a=read(),b=read(),Union(a,b);
             maxr=max(maxr,max(a,b));
         }
         f(i,,maxr)ans=max(ans,cnt[i]);
         pf("%d\n",ans);
     }
  }