【HDU】5604 merge【set练习题】

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题目链接：merge
set练习题
#include <stdio.h>#include <string.h>#include <set>#include <algorithm>using namespace std ;#define clr( a , x ) memset ( a , x , sizeof a  )const int MAXN = 300005 ;set < int > s[MAXN] ;set < int > :: iterator it ;int p[MAXN] ;int n , m ;int find ( int x ) {    int o = x , tmp ;    while ( o != p[o] ) o = p[o] ;    while ( x != p[x] ) {        tmp = p[x] ;        p[x] = o ;        x = tmp ;    }    return o ;}void solve () {    int x , y ;    scanf ( "%d" , &n ) ;    for ( int i = 1 ; i <= n ; ++ i ) {        p[i] = i ;        s[i].clear () ;        s[i].insert ( i << 1 ) ;    }    for ( int i = 1 ; i < n ; ++ i ) {        scanf ( "%d%d" , &x , &y ) ;        x = find ( x ) ;        y = find ( y ) ;        if ( s[x].size () > s[y].size () ) swap ( x , y ) ;        p[x] = y ;        for ( it = s[x].begin () ; it != s[x].end () ; ++ it ) {            s[y].insert ( *it ) ;        }        int l = *( s[y].begin () ) ;        int r = *( --s[y].end () ) ;        int m = ( l + r ) >> 1 ;        it = s[y].upper_bound ( m ) ;        int b = *it ;        int a = *( -- it ) ;        int t = ( a + b ) / 2 ;        int ans = max ( t - l , r - t ) ;        if ( it != s[y].begin () ) {            -- it ;            int z = *it ;            ++ it ;            t = ( a + z ) / 2 ;            ans = min ( ans , max ( t - l , r - t ) ) ;        }        ++ it ;        ++ it ;        if ( it != s[y].end () ) {            int z = *it ;            t = ( b + z ) / 2 ;            ans = min ( ans , max ( t - l , r - t ) ) ;        }        printf ( "%.1f\n" , ans / 2.0 ) ;    }}int main () {    int T ;    scanf ( "%d" , &T ) ;    for ( int i = 1 ; i <= T ; ++ i ) {        solve () ;    }    return 0 ;}
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