Maximum field and -- gss1 mushroom orz

Too much naive = as a knowledge point to sum up. Merge. For the maximum field and of an interval, you can separate the subsegments and of the two intervals below, or add the left side of the interval to the right side. Then let's figure out =

#include <iostream>#include <cstdio>#include <algorithm>#include <cstring>using namespace std;typedef long long ll;const ll maxn = 3000100;ll lson[maxn], rson[maxn], lm[maxn], rm[maxn], mans[maxn], sum[maxn];ll ne = 0, root;ll build(ll l, ll r) {    ll now = ++ ne;    if(l ^ r) {        ll mid = (l + r) >> 1;        lson[now] = build(l, mid);        rson[now] = build(mid + 1, r);    }    return now;}void update(ll now) {    if(lson[now]) {        sum[now] = sum[lson[now]] + sum[rson[now]];        lm[now] = max(lm[lson[now]], sum[lson[now]] + lm[rson[now]]);        rm[now] = max(rm[rson[now]], sum[rson[now]] + rm[lson[now]]);        mans[now] = max(max(mans[lson[now]], mans[rson[now]]), lm[rson[now]] + rm[lson[now]]);    }}void insert(ll now, ll l, ll r, ll v, ll pos) {    if(l == r) {        sum[now] = lm[now] = rm[now] = mans[now] = v;    }    else {        ll mid = (l + r) >> 1;        if(pos <= mid) insert(lson[now], l, mid, v, pos);        else insert(rson[now], mid + 1, r, v, pos);        update(now);    }}ll ask(ll now, ll l, ll r, ll ls, ll rs) {    ll ret;    if(l == ls && r == rs) ret = now;    else {        ll mid = (l + r) >> 1;        if(rs <= mid) ret = ask(lson[now], l, mid ,ls, rs);        else if(ls >= mid + 1) ret = ask(rson[now], mid + 1, r, ls, rs);        else {            ret = ++ ne;            ll rl = ask(lson[now], l, mid, ls, mid);            ll rr = ask(rson[now], mid + 1, r, mid + 1, rs);            lson[ret] = rl, rson[ret] = rr;            update(ret);        }    }    return ret;}ll ll_get() {    ll x = 0; char c = (char)getchar(); bool flag = 0;    while(!isdigit(c) && c != ‘-‘) c = (char)getchar();    if(c == ‘-‘) flag = 1;    while(!isdigit(c)) c = (char)getchar();    while(isdigit(c)) {        x = x * 10 + (ll)(c - ‘0‘);        c = (char)getchar();    }    if(flag) x = -x;    return x;}ll n, m;void sov() {    n = ll_get(); root = build(1, n);    for(ll i = 1; i <= n; ++ i) {        ll a = ll_get();        insert(root, 1, n, a, i);    }    m = ll_get();    while(m --) {        ll ls, rs; ls = ll_get(), rs = ll_get();        ll ans = ask(root, 1, n, ls, rs);        printf("%lld\n", mans[ans]);    }}int main() {    //freopen("test.in", "r", stdin);    //freopen("b.out", "w", stdout);    sov();    return 0;}

 

Maximum field and -- gss1 mushroom orz