Description
Kevin Sun wants to move his precious collection of n cowbells from Naperthrill to Exeter, where there is actually grass instead of corn. Before moving, he must pack his cowbells into k boxes of a fixed size. In order to keep his collection safe during transportation, he won‘t place more than two cowbells into a single box. Since Kevin wishes to minimize expenses, he is curious about the smallest size box he can use to pack his entire collection.
Kevin is a meticulous cowbell collector and knows that the size of his i-th (1 ≤ i ≤ n) cowbell is an integer si. In fact, he keeps his cowbells sorted by size, so si - 1 ≤ si for any i > 1. Also an expert packer, Kevin can fit one or two cowbells into a box of size s if and only if the sum of their sizes does not exceed s. Given this information, help Kevin determine the smallest s for which it is possible to put all of his cowbells into k boxes of size s.
Input
The first line of the input contains two space-separated integers n and k (1 ≤ n ≤ 2·k ≤ 100 000), denoting the number of cowbells and the number of boxes, respectively.
The next line contains n space-separated integers s1, s2, ..., sn (1 ≤ s1 ≤ s2 ≤ ... ≤ sn ≤ 1 000 000), the sizes of Kevin‘s cowbells. It is guaranteed that the sizes si are given in non-decreasing order.
Output
Print a single integer, the smallest s for which it is possible for Kevin to put all of his cowbells into k boxes of size s.
Sample Input
Hint
In the first sample, Kevin must pack his two cowbells into the same box.
In the second sample, Kevin can pack together the following sets of cowbells: {2, 3}, {5} and {9}.
In the third sample, the optimal solution is {3, 5} and {7}.
贪心，读入的数据已经排好，单独装一个的箱子装最大的，要装两个的箱子，必然装剩下的里面最大的和最小的，第二大和第二小……
#include<stdio.h>
#include<algorithm>
using namespace std;
long long n,k,s[100005],maxs;
int main(){
scanf("%lld%lld",&n,&k);
for(long long i=0;i<n;i++)
scanf("%lld",&s[i]);
maxs=s[n-1];
for(long long i=0;i<n-k;i++)
maxs=max(maxs,s[i]+s[(n-k)*2-i-1]);
printf("%lld\n",maxs);
return 0;
}
【Virtual Judge】F - 一般水的题1-More Cowbe
原文：http://www.cnblogs.com/flipped/p/5045348.html