UVA - 11729 - Commando War

http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=117&page=show_problem&problem=2829

题意：

有n个部下要布置，每个部下需要有对应的交待时间及任务时间，选择适当的交待顺序，以获取最小的总花费时间。

分析：

解决问题的方法不是直接模拟，而是通过数学的分析得出规律，这才是正确的思路方向；重点在于把情况正确地分类，接着进行分析。

#include <cstdio>
#include <iostream>
#include <string.h>
#include <algorithm>
#include <stdio.h>
using namespace std;

// #define LOCAL_TEST

const int MAX_SIZE = 1000+1;

struct Soldier
{
int m_brief;
int m_job;
};

Soldier szSoldiers[MAX_SIZE];

int fun_compare(const void*a, const void* b)
{
return ((Soldier*)b)->m_job - ((Soldier*)a)->m_job;
}

int main()
{
#ifdef LOCAL_TEST
freopen("f:\\in.txt", "r", stdin);
// 	freopen("f:\\out.txt", "w+", stdout);
#endif
int nSoldiers;
int nCase = 0;

// 	while ( scanf("%d", &nSoldiers) == 1 && nSoldiers )
while ( cin >>nSoldiers )
{
if ( nSoldiers == 0 )
break;
nCase++;

memset(szSoldiers, 0, MAX_SIZE * sizeof(Soldier));
for ( int i=0; i<nSoldiers; i++ )
cin >>szSoldiers[i].m_brief >> szSoldiers[i].m_job;
qsort(szSoldiers, nSoldiers, sizeof(szSoldiers[0]), fun_compare);

// one method
int totalTime = 0;
int remainTime = 0;
for ( int i=0; i<nSoldiers; i++ )
{
totalTime += szSoldiers[i].m_brief;

if ( (szSoldiers[i].m_brief + szSoldiers[i].m_job) > remainTime )
{
remainTime = szSoldiers[i].m_job;
} // end if
else
{
remainTime -= szSoldiers[i].m_brief;
} // end else
if ( remainTime < 0 )
{
cout <<"error" <<endl;
} // end if
} // end for
totalTime += remainTime;
cout <<"Case " <<nCase <<": " <<totalTime <<'\n';
// another method-----------------------------------------------------(Best)
// 		int totalTime = 0;
// 		int remainTime = 0;
// 		int sum = 0;
// 		int ans = 0;
// 		for ( int i=0; i<nSoldiers; i++ )
// 		{
// 			sum += szSoldiers[i].m_brief;
// 			ans = max(ans, sum+szSoldiers[i].m_job);
// 		} // end for
// 		cout <<"Case " <<nCase <<": " <<ans <<'\n';
} // end while

return 0;
}