UVA 11729-Commando War（排序分任务）

Commando War

“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 seeThe 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. Youhave a commando squad at your disposal and planning an ambush on an important enemy camplocated nearby. You have N soldiers in your squad. In your master-plan, every
single soldier has aunique responsibility and you don’t want any of your soldier to know the plan for other soldiers so thateveryone can focus on his task only. In order to enforce this, you brief every individual soldier abouthis tasks separately and just
before sending him to the battlefield. You know that every single soldierneeds a certain amount of time to execute his job. You also know very clearly how much time youneed to brief every single soldier. Being anxious to finish the total operation as soon
as possible, youneed to find an order of briefing your soldiers that will minimize the time necessary for all the soldiersto complete their tasks. You may assume that, no soldier has a plan that depends on the tasks of hisfellows. In other words, once a soldier
begins a task, he can finish it without the necessity of pausingin 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 twointegers B (1 ≤ B ≤ 10000) & J (1 ≤ J ≤ 10000). B seconds
are needed to brief the soldier whilecompleting his job needs J seconds. The end of input will be denoted by a case with N = 0. This caseshould 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 thetotal number of seconds counted from the start of your first briefing till the completion of all jobs.

Sample Input

3
2 5
3 2
2 1
3
3 3
4 4
5 5
3
1 10
1 9
1 8
0

题目意思：

你有N个部下，每个人需要完成一项任务。第i个部下需要你花Bi分钟交代任务，然后他会立刻独立且无间断的执行Ji分钟后完成任务。你需要选择交代任务的顺序，使得所有任务尽早执行完毕（最后一个执行完的任务应该尽早结束）。注意：不能同时给两个部下交代任务，但是部下们可以同时执行他们的任务。求所有任务完成的最短时间。

解题思路：

按照J从大到小的顺序给各个任务排序，然后依次交待。

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
#define maxn 20010
struct N
{
int b,j;//交代、执行
};
N a[maxn];
int cmp(N x,N y)//结构体排序
{
return (x.j>y.j);//大到小
}
int main()
{
int n,ca=0;
while(scanf("%d",&n)&&n!=0)
{
int t=0,ans=0;
for(int i=0; i<n; ++i)
scanf("%d%d",&a[i].b,&a[i].j);
sort (a,a+n,cmp);
for(int i=0; i<n; ++i)
{
t+=a[i].b;
ans=max(ans,t+a[i].j);
}
printf("Case %d: %d\n",++ca,ans);
}
return 0;
}
/*
3 2 5 3 2 2 1 3 3 3 4 4 5 5 3 1 10 1 9 1 8 0
*/