hdu 1856 离散化+并查集

注意n=0的情况

#include<iostream>
#include<cstring>
#include<cstdlib>
#include<cstdio>
#include<cmath>
#include<string>
#include<map>
#include<set>
#include<algorithm>
#include<vector>
#include<queue>
#include<stack>
#include<sstream>
#define LL long long
#define OJ_DEBUG 0
#define READ_FILE 1
using namespace std;
const int NN_MAX = 200010;
const int MM_MAX = 100010;
const int INF = 0x3fffffff;
/**********************************************************/
int p[NN_MAX],num[NN_MAX];
map<int,int> mapID;
/**********************************************************/
int min_2 (int x,int y) {return x<y?x:y;}
int max_2 (int x,int y) {return x>y?x:y;}
void swap (int& a, int& b){a^=b;b^=a;a^=b;}
int find (int i){return i==p[i]?i:p[i]=find (p[i]);}
void merge (int& i,int& j)
{
int x=find (i), y=find (j);
if (x!=y) p[x]=y;
}
/**********************************************************/
int main()
{
if (READ_FILE) freopen ("in.txt","r",stdin);
int n;
while (scanf ("%d",&n)!=EOF)
{
if (n==0){printf ("1\n");continue;}
int a,b;
int len=1;
for (int i=0;i<NN_MAX;i++) p[i]=i;
memset (num,0,sizeof (num));
mapID.clear ();
for (int i=0;i<n;i++){
scanf ("%d %d",&a,&b);
if (mapID.count (a)==0) mapID[a]=len++;
if (mapID.count (b)==0) mapID[b]=len++;
merge (mapID[a],mapID[b]);
}
for (int i=1;i<len;i++)
num[find (i)]++;
int mx=0;
for (int i=1;i<len;i++)
mx=(mx<num[i]?num[i]:mx);
printf ("%d\n",mx);
}
return 0;
}