最小生成树中的最长边,地址: http://acm.pku.edu.cn/JudgeOnline/problem?id=1861
#include <stdio.h>
#include <stdlib.h>

const int LEN = 15005;

struct segment
  {
int b;
int e;
int len;
}seg[LEN];//线段

int used[LEN];

void init ( int n )
  {
for ( int i=0; i<n; i++ )
 {
used[i] = 0;
}
}

//并查集部分
int fa[LEN/10];

void make ( int n )
  {

for ( int i=0; i<n; i++ )
 {
fa[i] = -1;
}
}

int find ( int a )
  {

if ( fa[a]<0 )
 {
return a;
}

int r = find ( fa[a] );
fa[a] = r;
return r;
}

void un ( int a, int b )
  {

int ra = find ( a );
int rb = find ( b );

if ( fa[ra]<fa[rb] )
 {
fa[ra] += fa[rb];
fa[rb] = ra;
}
else
 {
fa[rb] += fa[ra];
fa[ra] = rb;
}
}

//主要处理部分

int cmp ( const void *a, const void *b )
  {

return ( (segment *)a )->len - ( (segment *)b )->len;
}

void kul ( int n, int m )
  {

qsort ( seg, m, sizeof ( segment ), cmp );

int max = -1;
int count = 0;
init ( n );
make ( n );
for ( int i=0; i<m; i++ )
 {
if ( find ( seg[i].b )!=find ( seg[i].e ) )
 {
un ( seg[i].b, seg[i].e );

used[i] = 1;
count ++;
if ( max < seg[i].len )
 {
max = seg[i].len;
}
}
}

printf ( "%d\n%d\n", max, count );
for ( int i=0; i<m; i++ )
 {
if ( used[i] )
 {
printf ( "%d %d\n", seg[i].b+1, seg[i].e+1 );
}
}
}

int main ()
  {

int n, m;
int b, e, len;

while ( scanf ( "%d%d", &n, &m ) != EOF )
 {
for ( int i=0; i<m; i++ )
 {
scanf ( "%d%d%d", &b, &e, &len );
seg[i].b = b-1<e-1 ? b-1:e-1;
seg[i].e = b-1>e-1 ? b-1:e-1;
seg[i].len = len;
}

kul ( n, m );
}
return 0;
}

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