UVA 1149 Bin Packing

分析

至多俩，大小配。

代码

#include <cstdio>
#include <algorithm>
#define MAX_N 100005
using std::sort;

int N, L, A[MAX_N];

void solve()
{
    sort(A, A+N);
    int l = 0, r = N-1, a = 0;
    while (l <= r)
        if (A[l] + A[r] <= L) { a++; l++; r--; }
        else { a++; r--; }
    printf("%d\n", a);
}

int main()
{
    int T;
    scanf("%d", &T);
    while (T--) {
        scanf("%d%d", &N, &L);
        for (int i = 0; i < N; i++) scanf("%d", &A[i]);
        solve();
        if (T) printf("\n");
    }
    return 0;
}

题目

Description

A set of $n$ 1-dimensional items have to be packed in identical bins. All bins have exactly the same length $l$ and each item $i$ has length $l_i \le l$. We look for a minimal number of bins $q$ such that

• each bin contains at most 2 items,
• each item is packed in one of the $q$ bins,
  • the sum of the lengths of the items packed in a bin does not exceed $l$.

  You are requested, given the integer values $n$ , $l$ , $l_1$ , …, $l_n$ , to compute the optimal number of bins $q$.

  Input

  The input begins with a single positive integer on a line by itself indicating the number of the cases following, each of them as described below. This line is followed by a blank line, and there is also a blank line between two consecutive inputs.

  The first line of the input file contains the number of items $n$($1 \le n \le 10_5$) . The second line contains one integer that corresponds to the bin length $l \le 10000$. We then have lines containing one integer value that represents the length of the items.

Output

For each test case, the output must follow the description below. The outputs of two consecutive cases will be separated by a blank line.

For each input file, your program has to write the minimal number of bins required to pack all items.

Sample Input

1

10
80
70
15
30
35
10
80
20
35
10
30

Sample Output

6