BZOJ 1787: [Ahoi2008]Meet 紧急集合( 树链剖分 )

这道题用 LCA 就可以水过去 , 但是我太弱了 QAQ 倍增写LCA总是写残...于是就写了树链剖分...

其实也不难写 , 线段树也不用用到 , 自己YY一下然后搞一搞就过了...速度还挺快的好像= = #9

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#include<cstdio>

#include<cstring>

#include<algorithm>

#include<iostream>

 

#define rep( i , n ) for( int i = 0 ; i < n ; i++ )

#define clr( x , c ) memset( x , c , sizeof( x ) )

#define REP( x ) for( edge* e = head[ x ] ; e ; e = e -> next )

 

using namespace std;

 

const int maxn = 500000 + 5;

 

struct edge {

int to;

edge* next;

};

 

edge* pt , EDGE[ maxn << 1 ];

edge* head[ maxn ];

 

void edge_init() {

pt = EDGE;

clr( head , 0 );

}

 

void add( int u , int v ) {

pt -> to = v;

pt -> next = head[ u ];

head[ u ] = pt++;

}

#define add_edge( u , v ) add( u , v ) , add( v , u )

 

 

int fa[ maxn ] , top[ maxn ] , size[ maxn ] , son[ maxn ] , dep[ maxn ];

int id[ maxn ] , _id[ maxn ] , id_cnt = 0 , TOP;

 

void dfs( int x ) {

size[ x ] = 1;

son[ x ] = -1;

REP( x ) {

int to = e -> to;

if( to == fa[ x ] ) continue;

dep[ to ] = dep[ x ] + 1;

fa[ to ] = x;

dfs( to );

size[ x ] += size[ to ];

if( son[ x ] == - 1 || size[ to ] > size[ son[ x ] ] )

   son[ x ] = to;

}

}

 

void DFS( int x ) {

top[ x ] = TOP;

id[ x ] = ++id_cnt;

_id[ id_cnt ] = x;

if( son[ x ] != -1 )

   DFS( son[ x ] );

REP( x ) if( id[ e -> to ] < 0 )

   DFS( TOP = e -> to );

}

 

void DFS_init() {

clr( id , -1 );

dfs( dep[ 0 ] = 0 );

DFS( TOP = 0 );

}

 

int Q_LCA( int x , int y ) {

while( top[ x ] != top[ y ] ) {

if( dep[ top[ x ] ] < dep[ top[ y ] ] ) 

   swap( x , y );

x = fa[ top[ x ] ];

}

return dep[ x ] < dep[ y ] ? x : y;

}

 

int Q_dist( int x , int y ) {

int res = 0;

while( top[ x ] != top[ y ] ) {

if( dep[ top[ x ] ] < dep[ top[ y ] ] )

   swap( x , y );

res += id[ x ] - id[ top[ x ] ];

x = fa[ top[ x ] ];

res++;

}

if( dep[ x ] < dep[ y ] )

   swap( x , y );

return res + id[ x ] - id[ y ];

}

 

 

int ans[ 2 ];

void work( int x , int y , int z ) {

int LCA[ 3 ] = { Q_LCA( x , y ) , Q_LCA( x , z ) , Q_LCA( y , z ) };

if( LCA[ 0 ] == LCA[ 1 ] )

   ans[ 0 ] = LCA[ 2 ];

else if( LCA[ 0 ] == LCA[ 2 ] )

   ans[ 0 ] = LCA[ 1 ];

else 

   ans[ 0 ] = LCA[ 0 ];

ans[ 1 ] = Q_dist( x , ans[ 0 ] ) + Q_dist( y , ans[ 0 ] ) + Q_dist( z , ans[ 0 ] );

}

 

inline int read() {

int res = 0;

char c = getchar();

while( ! isdigit( c ) ) c = getchar();

while( isdigit( c ) ) {

res = res * 10 + c - '0';

c = getchar();

}

return res;

}

 

int main() {

freopen( "test.in" , "r" , stdin );

int n = read() , m = read();

edge_init();

rep( i , n - 1 ) {

int u = read() , v = read();

u-- , v--;

add_edge( u , v );

}

DFS_init();

while( m-- ) {

int x = read() , y = read() , z = read();

x-- , y-- , z--;

work( x , y , z );

printf( "%d %d\n" , ans[ 0 ] + 1 , ans[ 1 ] );

}

return 0;

}

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1787: [Ahoi2008]Meet 紧急集合

Time Limit: 20 Sec  Memory Limit: 162 MB
Submit: 1542  Solved: 683
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Description

Input

Output

Sample Input

6 4
1 2
2 3
2 4
4 5
5 6
4 5 6
6 3 1
2 4 4
6 6 6

Sample Output

5 2
2 5
4 1
6 0

HINT

Source

Day1