Minimum

给一个数组，有两种操作
1：求 x,y in [l,r]，MinAx∗Ay
2：将 Ax替换值为 v

挺显然的线段树，分别求区间最大和最小值，如果区间最小值是正数，那么直接是这个数的平方。否则就要看看最大值，如果最大值是正数，那么就是最小值乘最大值（因为是负数），否则的话就是最大值的平方（因为出来是正数）。

#include <bits/stdc++.h>using namespace std;const int maxn = 800010, maxx = 0x3f3f3f3f, minn = -0x3f3f3f3f;struct Node {    int f, s;    Node() {}    Node(int ff, int ss): f(ff), s(ss) {}};int a[maxn], b[maxn], n, m, x, y, l, r, op;void _clear(int x, int l, int r) {    b[x] = minn;    a[x] = maxx;    if (l == r) return;    int mid = (l+r)/2;    _clear(x*2, l, mid);    _clear(x*2+1, mid+1, r);}void init() {    _clear(1, 1, n);}void a_insert(int x, int l, int r, int t, int v) {    if (l == r) {        a[x] = v; return;    }    int mid = (l+r)/2;    if (t <= mid) a_insert(x*2, l, mid, t, v);    else a_insert(x*2+1, mid+1, r, t, v);    a[x] = min(a[x*2], a[x*2+1]);}void b_insert(int x, int l, int r, int t, int v) {    if (l == r) {        b[x] = v; return;    }    int mid = (l+r)/2;    if (t <= mid) b_insert(x*2, l, mid, t, v);    else b_insert(x*2+1, mid+1, r, t, v);    b[x] = max(b[x*2], b[x*2+1]);}int a_find(int x, int l, int r, int ll, int rr) {    if (l == ll && r == rr) return a[x];    int mid = (l+r)/2;    if (rr <= mid) return a_find(x*2, l, mid, ll, rr);    else if (ll > mid) return a_find(x*2+1, mid+1, r, ll, rr);    else {        int temp = a_find(x*2, l, mid, ll, mid);        temp = min(temp, a_find(x*2+1, mid+1, r, mid+1, rr));        return temp;    }}int b_find(int x, int l, int r, int ll, int rr) {    if (l == ll && r == rr) return b[x];    int mid = (l+r)/2;    if (rr <= mid) return b_find(x*2, l, mid, ll, rr);    else if (ll > mid) return b_find(x*2+1, mid+1, r, ll, rr);    else {        int temp = b_find(x*2, l, mid, ll, mid);        temp = max(temp, b_find(x*2+1, mid+1, r, mid+1, rr));        return temp;    }}int main() {    freopen("input.txt","r",stdin);    int T;    scanf("%d", &T);    while (T--) {        scanf("%d", &m);        n = 1;        for (int i = 1; i <= m; i++) n *= 2;        init();        for (int i = 1; i <= n; i++) {            scanf("%d", &x);            a_insert(1, 1, n, i, x);            b_insert(1, 1, n, i, x);        }        scanf("%d", &m);        for (int i = 1; i <= m; i++) {            scanf("%d %d %d", &op, &l, &r);            if (op == 1) {                l++; r++;                if (l == r) {                    long long ans = b_find(1, 1, n, l, r);                    printf("%lld\n", ans*ans);                } else {                    long long ans_l = a_find(1, 1, n, l, r);                    long long ans_r = b_find(1, 1, n, l, r);                    if (ans_l >= 0) printf("%lld\n", ans_l*ans_l);                    else {                        if (ans_r >= 0) printf("%lld\n", ans_l*ans_r);                        else printf("%lld\n", ans_r*ans_r);                    }                }            } else {                l++;                a_insert(1, 1, n, l, r);                b_insert(1, 1, n, l, r);            }        }    }}