BZOJ 1651: [Usaco2006 Feb]Stall Reservations 专用牛棚( 线段树 )

线段树..

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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 L( x ) ( x << 1 )

#define R( x ) ( L( x ) ^ 1 )

#define LC( x ) tree[ L( x ) ]

#define RC( x ) tree[ R( x ) ]

#define mid( l , r ) ( ( l + r ) >> 1 )

 

using namespace std;

 

const int n = 1000000;

 

struct Node {

int l , r;

int Max , add;

Node() : Max( 0 ) , add( 0 ) { }

};

 

Node tree[ n << 2 ];

 

void maintain( int x ) {

Node &o = tree[ x ];

o.Max = 0;

if( o.r > o.l )

   o.Max = max( LC( x ).Max , RC( x ).Max );

   

o.Max += o.add;

}

 

int L , R;

 

void update( int x ) {

Node &o = tree[ x ];

if( L <= o.l && o.r <= R ) 

   

   o.add += 1;

   

else {

int m = mid( o.l , o.r );

if( L <= m ) update( L( x ) );

if( m < R ) update( R( x ) );

}

maintain( x );

}

 

void build( int x , int l , int r ) {

Node &o = tree[ x ];

o.l = l , o.r = r;

if( l == r )

   return ;

   

int m = mid( l , r );

build( L( x ) , l , m );

build( R( x ) , m + 1 , r );

} 

int main() {

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

int m;

cin >> m;

build( 1 , 1 , n );

while( m-- ) {

scanf( "%d%d" , &L , &R );

update( 1 );

}

printf( "%d\n" , tree[ 1 ].Max );

return 0;

}

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1651: [Usaco2006 Feb]Stall Reservations 专用牛棚

Time Limit: 10 Sec  Memory Limit: 64 MB
Submit: 587  Solved: 327
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Description

Oh those picky N (1 <= N <= 50,000) cows! They are so picky that each one will only be milked over some precise time interval A..B (1 <= A <= B <= 1,000,000), which includes both times A and B. Obviously, FJ must create a reservation system to determine which stall each cow can be assigned for her milking time. Of course, no cow will share such a private moment with other cows. Help FJ by determining: * The minimum number of stalls required in the barn so that each cow can have her private milking period * An assignment of cows to these stalls over time

有N头牛,每头牛有个喝水时间,这段时间它将专用一个Stall 现在给出每头牛的喝水时间段,问至少要多少个Stall才能满足它们的要求

Input

* Line 1: A single integer, N

* Lines 2..N+1: Line i+1 describes cow i's milking interval with two space-separated integers.

Output

* Line 1: The minimum number of stalls the barn must have.

* Lines 2..N+1: Line i+1 describes the stall to which cow i will be assigned for her milking period.

Sample Input

5
1 10
2 4
3 6
5 8
4 7

Sample Output

4

OUTPUT DETAILS:

Here's a graphical schedule for this output:

Time 1 2 3 4 5 6 7 8 9 10
Stall 1 c1>>>>>>>>>>>>>>>>>>>>>>>>>>>
Stall 2 .. c2>>>>>> c4>>>>>>>>> .. ..
Stall 3 .. .. c3>>>>>>>>> .. .. .. ..
Stall 4 .. .. .. c5>>>>>>>>> .. .. ..

Other outputs using the same number of stalls are possible.

HINT

不妨试下这个数据,对于按结束点SORT,再GREEDY的做法 1 3 5 7 6 9 10 11 8 12 4 13 正确的输出应该是3

Source

Silver