poj2549

排序题

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#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <algorithm>
using namespace std;

#define maxn 1005
#define inf 0x3f3f3f3f

struct A
{
    int a, b;
    int v;
} add[maxn * maxn];

struct B
{
    int c, d;
    int v;
} mns[maxn * maxn];

int f[maxn];
int n;
int n1, n2;

bool operator <(const A &a, const A &b)
{
    return a.v < b.v;
}

bool operator <(const B &a, const B &b)
{
    return a.v < b.v;
}

void input()
{
    for (int i = 0; i < n; i++)
        scanf("%d", &f[i]);
}

void make()
{
    n1 = n2 = 0;
    for (int i = 0; i < n - 1; i++)
        for (int j = i + 1; j < n; j++)
        {
            add[n1].a = f[i];
            add[n1].b = f[j];
            add[n1].v = f[i] + f[j];
            n1++;
        }
    for (int i = 0; i < n - 1; i++)
        for (int j = i + 1; j < n; j++)
        {
            mns[n2].d = max(f[i], f[j]);
            mns[n2].c = min(f[j], f[i]);
            mns[n2].v = abs(f[i] - f[j]);
            n2++;
        }
}

bool ok(int a, int b, int c, int d)
{
    return a != b && a != c && a != d && b != c && b != d && c != d;
}

void work()
{
    int temp = 0;
    int ans = -inf;
    for (int i = 0; i < n2; i++)
    {
        if (mns[i].d < ans)
            continue;
        while (add[temp].v < mns[i].v)
            temp++;
        int j = temp;
        while (j < n1 && add[j].v == mns[i].v)
        {
            if (ok(add[j].a, add[j].b, mns[i].c, mns[i].d))
            {
                ans = max(ans, mns[i].d);
                break;
            }
            j++;
        }
    }
    if (ans == -inf)
        printf("no solution\n");
    else
        printf("%d\n", ans);
}

int main()
{
    //freopen("t.txt", "r", stdin);
    while (scanf("%d", &n), n)
    {
        input();
        make();
        sort(add, add + n1);
        sort(mns, mns + n2);
        work();
    }
    return 0;
}