Description
給定一個序列,每次詢問區間 [l,r] [ l , r ] 内,所有權值與其出現次數的乘積的最大值。
Solution
復原莫隊模闆題。
将詢問以左端點所在塊為第一關鍵字,右端點為第二關鍵字排序。
直接莫隊、用
std::set
維護是 O(nn‾√logn) O ( n n log n ) 的。
對于所有左端點所在塊相同的詢問,右端點都是遞增的,我們從該塊的右端點依次向每個詢問的右端點擴充,處理每次詢問時,将左端向左移動得到答案後還原即可。
通過復原莫隊,我們可以将很多 O(nn‾√logn) O ( n n log n ) 的莫隊優化成 O(nn‾√) O ( n n ) 。
Code
/************************************************
* Au: Hany01
* Date: Aug 25th, 2018
* Prob: BZOJ4241 曆史研究
* Email: [email protected] & [email protected]
* Inst: Yali High School
************************************************/
#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef long double LD;
typedef pair<int, int> PII;
#define rep(i, j) for (register int i = 0, i##_end_ = (j); i < i##_end_; ++ i)
#define For(i, j, k) for (register int i = (j), i##_end_ = (k); i <= i##_end_; ++ i)
#define Fordown(i, j, k) for (register int i = (j), i##_end_ = (k); i >= i##_end_; -- i)
#define Set(a, b) memset(a, b, sizeof(a))
#define Cpy(a, b) memcpy(a, b, sizeof(a))
#define x first
#define y second
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define SZ(a) ((int)(a).size())
#define INF (0x3f3f3f3f)
#define INF1 (2139062143)
#define debug(...) fprintf(stderr, __VA_ARGS__)
#define y1 wozenmezhemecaia
template <typename T> inline bool chkmax(T &a, T b) { return a < b ? a = b, : ; }
template <typename T> inline bool chkmin(T &a, T b) { return b < a ? a = b, : ; }
inline int read() {
static int _, __; static char c_;
for (_ = , __ = , c_ = getchar(); c_ < '0' || c_ > '9'; c_ = getchar()) if (c_ == '-') __ = -;
for ( ; c_ >= '0' && c_ <= '9'; c_ = getchar()) _ = (_ << ) + (_ << ) + (c_ ^ );
return _ * __;
}
const int maxn = + ;
int n, q, a[maxn], ls[maxn], bk, num, bel[maxn], cur, tot;
LL ans[maxn];
struct Query { int id, l, r; } Q[maxn];
inline bool operator < (Query A, Query B) { return bel[A.l] == bel[B.l] ? A.r < B.r : A.l < B.l; }
inline void bfcalc(int t) {
static int cnt[maxn];
For(i, Q[t].l, Q[t].r)
++ cnt[a[i]], chkmax(ans[Q[t].id], (LL)cnt[a[i]] * ls[a[i]]);
For(i, Q[t].l, Q[t].r) -- cnt[a[i]];
}
inline void Solve(int lb) {
register int now = min(n, lb * bk), hxt = now + , hxt_ = hxt, cnt[maxn];
register LL Max_, Max;
Set(cnt, ), Max = ;
for (; cur <= n && bel[Q[cur].l] == lb; ++ cur) {
if (bel[Q[cur].l] == bel[Q[cur].r]) { bfcalc(cur); continue; }
while (now < Q[cur].r) ++ cnt[a[++ now]], chkmax(Max, (LL)cnt[a[now]] * ls[a[now]]);
for (Max_ = Max; hxt > Q[cur].l; ++ cnt[a[-- hxt]], chkmax(Max_, (LL)cnt[a[hxt]] * ls[a[hxt]]));
ans[Q[cur].id] = Max_;
while (hxt < hxt_) -- cnt[a[hxt ++]];
}
}
int main()
{
#ifdef hany01
freopen("bzoj4241.in", "r", stdin);
freopen("bzoj4241.out", "w", stdout);
#endif
n = read(), q = read();
For(i, , n) a[i] = ls[i] = read();
sort(ls + , ls + + n), tot = unique(ls + , ls + + n) - ls - ;
For(i, , n) a[i] = lower_bound(ls + , ls + + tot, a[i]) - ls;
For(i, , q) Q[i].id = i, Q[i].l = read(), Q[i].r = read();
bk = sqrt(n);
For(i, , n) bel[i] = (i - ) / bk + ;
num = bel[n], sort(Q + , Q + + q), cur = ;
For(i, , num) Solve(i);
For(i, , q) printf("%lld\n", ans[i]);
return ;
}