只是单纯晒晒两天才攻克的线段树代码（y总式码风真的优美）

#include <iostream>
#include <algorithm>

using namespace std;

const int N = 100010, INF = 0x3f3f3f3f;

typedef long long LL;

struct Tree
{
    int l, r;
    int maxz, minz, maxf, minf;
}tr1[N * 4], tr2[N * 4];

int n, m, q;
int a[N], b[N];

void pushup(Tree &p, Tree &l, Tree &r)
{
    p.maxz = max(l.maxz, r.maxz);
    p.minz = min(l.minz, r.minz);
    p.maxf = max(l.maxf, r.maxf);
    p.minf = min(l.minf, r.minf);
}

void build(Tree tr[], int w[], int p, int l, int r)
{
    if (l == r)
    {
        tr[p] = {l, r, -INF, INF, -INF, INF};
        if (w[r] >= 0) tr[p].maxz = tr[p].minz = w[r];
        if (w[r] <= 0) tr[p].maxf = tr[p].minf = w[r];
        return;
    }
    tr[p] = {l, r};
    int mid = l + r >> 1;
    build(tr, w, p << 1, l, mid), build(tr, w, p << 1 | 1, mid + 1, r);
    pushup(tr[p], tr[p << 1], tr[p << 1 | 1]);
}

Tree query(Tree tr[], int p, int l, int r)
{
    if (l <= tr[p].l && r >= tr[p].r) return tr[p];
    else
    {
        int mid = tr[p].l + tr[p].r >> 1;
        if (l > mid) return query(tr, p << 1 | 1, l, r);
        if (r <= mid) return query(tr, p << 1, l, r);
        Tree res, L = query(tr, p << 1, l, r), R = query(tr, p << 1 | 1, l, r);
        pushup(res, L, R);
        return res;
    }
}

int main()
{
    scanf("%d%d%d", &n, &m, &q);
    for (int i = 1; i <= n; i ++ ) scanf("%d", &a[i]);
    for (int i = 1; i <= m; i ++ ) scanf("%d", &b[i]);

    build(tr1, a, 1, 1, n), build(tr2, b, 1, 1, m);

    while (q -- )
    {
        int l1, r1, l2, r2;
        scanf("%d%d%d%d", &l1, &r1, &l2, &r2);
        Tree t1 = query(tr1, 1, l1, r1), t2 = query(tr2, 1, l2, r2);
        LL res;
        if (t2.minf == INF)
        {
            if (t1.minz != INF) res = (LL)t1.maxz * t2.minz;
            else res = (LL)t1.maxf * t2.maxz;
        }
        else if (t2.minz == INF)
        {
            if (t1.minf != INF) res = (LL)t1.minf * t2.maxf;
            else res = (LL)t1.minz * t2.minf;
        }
        else
        {
            if (t1.minz == INF) res = (LL)t1.maxf * t2.maxz;
            else if (t1.minf == INF) res = (LL)t1.minz * t2.minf;
            else res = max((LL)t1.maxf * t2.maxz, (LL)t1.minz * t2.minf);
        }
        printf("%lld\n", res);
    }

    return 0;
}