UVA 11997 K Smallest Sums

[code]#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <string.h>
#include <queue>
#include <stack>
#include <vector>

using namespace std;

struct Item
{
    int s, b;
    Item(int s, int b) :s(s), b(b) {}
    bool operator < (const Item& rhs) const
    {
        return s > rhs.s;
    }
};

const int MAXN = 1100;
int a[MAXN][MAXN];
int b[MAXN];

void merge(int* A, int* B, int* C, int n)
{
    priority_queue<Item> q;
    for (int i = 0; i < n; i++)
        q.push(Item (A[i] + B[0], 0));
    for (int i = 0; i < n; i++)
    {
        Item item = q.top(); q.pop();
        C[i] = item.s;
        int b = item.b;
        if (b + 1 < n) q.push(Item(C[i] - B[b] + B[b+1], b + 1));
    }
}

int main()
{
    int n;
    while (scanf("%d", &n) != EOF)
    {
        for (int i = 0; i < n; i++)
        {
            for (int j = 0; j < n; j++)
                scanf("%d", &a[i][j]);
            sort(a[i], a[i] + n);
        }
        for (int i = 1; i < n; i++)
        {
            merge(a[0], a[i], b, n);
            for (int ii = 0; ii < n; ii++)
                a[0][ii] = b[ii];
        }
        printf("%d",a[0][0]);
        for (int i = 1; i < n; i++) printf(" %d",a[0][i]);
        printf("\n");
    }
    return 0;
}