UVA 11729-Commando War（排序分任務）

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

題目意思：

你有N個部下，每個人需要完成一項任務。第i個部下需要你花Bi分鐘交代任務，然後他會立刻獨立且無間斷的執行Ji分鐘後完成任務。你需要選擇交代任務的順序，使得所有任務儘早執行完畢（最後一個執行完的任務應該儘早結束）。注意：不能同時給兩個部下交代任務，但是部下們可以同時執行他們的任務。求所有任務完成的最短時間。

解題思路：

按照J從大到小的順序給各個任務排序，然後依次交待。

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
#define maxn 20010
struct N
{
    int b,j;//交代、執行
};
N a[maxn];
int cmp(N x,N y)//結構體排序
{
    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
*/