# BZOJ 1620: [Usaco2008 Nov]Time Management 时间管理( 二分答案 )

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#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cctype>
#include<iostream>

#define rep( i , n ) for( int i = 0 ;  i < n ; ++i )
#define clr( x , c ) memset( x , c , sizeof( x ) )

using namespace std;

const int maxn = 1000 + 5;

int n;

struct data {
int t , s;
scanf( "%d%d" , &t , &s );
}
bool operator < ( const data &rhs ) const {
return s < rhs.s;
}
};

data A[ maxn ];

bool jud( int cur ) {
rep( i , n ) {
data &x = A[ i ];
if( ( cur += x.t ) > x.s ) return false;
}
return true;
}

int main() {
// freopen( "test.in" , "r" , stdin );
cin >> n;
int L = 0 , R = 0x7fffffff;
rep( i , n ) {

R = min( A[ i ].s , R );

}
sort( A , A + n );
int ans = -1;
while( L <= R ) {
int mid = ( L + R ) >> 1;
if( jud( mid ) )
ans = mid , L = mid + 1;

else

R = mid - 1;
}
cout << ans << "\n";
return 0;
}

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## 1620: [Usaco2008 Nov]Time Management 时间管理

Time Limit: 5 Sec  Memory Limit: 64 MB
Submit: 539  Solved: 325
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## Description

Ever the maturing businessman, Farmer John realizes that he must manage his time effectively. He has N jobs conveniently numbered 1..N (1 <= N <= 1,000) to accomplish (like milking the cows, cleaning the barn, mending the fences, and so on). To manage his time effectively, he has created a list of the jobs that must be finished. Job i requires a certain amount of time T_i (1 <= T_i <= 1,000) to complete and furthermore must be finished by time S_i (1 <= S_i <= 1,000,000). Farmer John starts his day at time t=0 and can only work on one job at a time until it is finished. Even a maturing businessman likes to sleep late; help Farmer John determine the latest he can start working and still finish all the jobs on time.

## Input

* Line 1: A single integer: N

* Lines 2..N+1: Line i+1 contains two space-separated integers: T_i and S_i

## Output

* Line 1: The latest time Farmer John can start working or -1 if Farmer John cannot finish all the jobs on time.

## Sample Input

4
3 5
8 14
5 20
1 16

INPUT DETAILS:

Farmer John has 4 jobs to do, which take 3, 8, 5, and 1 units of
time, respectively, and must be completed by time 5, 14, 20, and
16, respectively.

## Sample Output

2

OUTPUT DETAILS:

Farmer John must start the first job at time 2. Then he can do
the second, fourth, and third jobs in that order to finish on time.

## Source

posted @ 2015-06-06 11:06  JSZX11556  阅读(220)  评论(0编辑  收藏  举报