UVA-11729 - Commando War-2014年4月19日112200

G	Commando War Input: Standard Input Output: Standard Output

 

 

“Waiting for orders we held in the wood, word from the front never came

By evening the sound of the gunfire was miles away

Ah softly we moved through the shadows, slip away through the trees

Crossing their lines in the mists in the fields on our hands and our knees

And all that I ever, was able to see

The fire in the air, glowing red, silhouetting the smoke on the breeze”

 

There is a war and it doesn't look very promising for your country. Now it's time to act. You have a commando squad at your disposal and planning an ambush on an important enemy camp located nearby. You have N soldiers in your squad. In your master-plan, every single soldier has a unique responsibility and you don't want any of your soldier to know the plan for other soldiers so that everyone can focus on his task only. In order to enforce this, you brief every individual soldier about his tasks separately and just before sending him to the battlefield. You know that every single soldier needs a certain amount of time to execute his job. You also know very clearly how much time you need to brief every single soldier. Being anxious to finish the total operation as soon as possible, you need to find an order of briefing your soldiers that will minimize the time necessary for all the soldiers to complete their tasks. You may assume that, no soldier has a plan that depends on the tasks of his fellows. In other words, once a soldier  begins a task, he can finish it without the necessity of pausing in between.

 

Input

 

There will be multiple test cases in the input file. Every test case starts with an integer N (1<=N<=1000), denoting the number of soldiers. Each of the following N lines describe a soldier with two integers B (1<=B<=10000) & J (1<=J<=10000). B seconds are needed to brief the soldier while completing his job needs J seconds. The end of input will be denoted by a case with N =0 . This case should not be processed.

 

Output

 

For each test case, print a line in the format, “Case X: Y”, where X is the case number & Y is the total number of seconds counted from the start of your first briefing till the completion of all jobs.

 

Sample Input          Output for Sample Input

3 2 5 3 2 2 1 3 3 3 4 4 5 5 0

Case 1: 8 Case 2: 15

Problem Setter: Mohammad Mahmudur Rahman, Special Thanks: Manzurur Rahman Khan

 

解题报告

时间较长的任务应该先交代。则应将执行时间按从小到大排序，然后依次交代

这样做的理由是

排序后，如果交换两个相邻的任务X和Y，不影响其他任务的完成时间

而且这两个任务的完成时间也是最短的

情况一：交换之前，Y比X先结束，交换后，时间变长

情况二：交换之前，X比Y先结束，交换后，时间变长

 

//2014年4月19日11:22:00

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

struct task
{
	int B;
	int J;
}v[1010];

int cmp(task a,task b)
{
	return  a.J>b.J;
}

int main()
{
	int N,B,J,i,kase = 1;
	while(scanf("%d",&N) == 1 && N)
	{
		memset(v,0,sizeof(v));
		for(i = 0; i < N; i++)
			scanf("%d%d",&v[i].B, &v[i].J);
		sort(v, v+N, cmp);
		int time_start = 0;
		int time_end = 0;
		for(i = 0; i < N; i++)
		{
			time_start += v[i].B;
			time_end = max(time_end, time_start + v[i].J);
		}
		printf("Case %d: %d\n", kase++, time_end);
	}
	return 0;
}