hdu 1856

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More is better

Time Limit: 5000/1000 MS (Java/Others) Memory Limit: 327680/102400 K (Java/Others)
Total Submission(s): 26043 Accepted Submission(s): 9341

Problem Description

Mr Wang wants some boys to help him with a project. Because the project is rather complex, the more boys come, the better it will be. Of course there are certain requirements.

Mr Wang selected a room big enough to hold the boys. The boy who are not been chosen has to leave the room immediately. There are 10000000 boys in the room numbered from 1 to 10000000 at the very beginning. After Mr Wang's selection any two of them who are still in this room should be friends (direct or indirect), or there is only one boy left. Given all the direct friend-pairs, you should decide the best way.

Input

The first line of the input contains an integer n (0 ≤ n ≤ 100 000) - the number of direct friend-pairs. The following n lines each contains a pair of numbers A and B separated by a single space that suggests A and B are direct friends. (A ≠ B, 1 ≤ A, B ≤ 10000000)

Output

The output in one line contains exactly one integer equals to the maximum number of boys Mr Wang may keep.

Sample Input

41 23 45 61 641 23 45 67 8

Sample Output

42
题意：简化成并查集问题，求每个连通块中，包含的元素的个数，输出最大的
#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>#define N 10000005using namespace std;int fa[N],num[N];int Max;int find(int x)           //找到父节点 {int a=x;while(x!=fa[x]){x=fa[x];}while(a!=fa[a])       //压缩路径，可以省略，可能会超时 {int z=a;a=fa[a];fa[z]=x;}return x; } void Union(int a,int b)  //合并节点 {int faa=find(a);int fab=find(b);if(faa!=fab){fa[faa]=fab;num[fab]=num[fab]+num[faa];}if(num[fab]>Max)Max=num[fab];}void init(int n)      //初始化 {for(int i=1;i<=n;i++){fa[i]=i;num[i]=1;}}int main(){int m;while(~scanf("%d",&m)){int a,b;init(N);Max=1;for(int i=1;i<=m;i++){scanf("%d %d",&a,&b);Union(a,b);}printf("%d\n",Max);}}

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