UOJ Logo

NOI.AC

IDProblemSubmitterResultTimeMemoryLanguageFile sizeSubmit timeJudge time
#213924#2380. 中位数N1001069ms5960kbC++111.9kb2024-11-14 19:09:242024-11-14 23:01:50

answer

//
//  na 2380.cpp
//  Competitive Programming
//
//  Created by m2 on 2024/11/14.
//

#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <string.h>
#include <vector>
using namespace std;
typedef long long int ll;
const int maxn = 3e5 + 5;
int n, a[maxn], vs[maxn], vl;
struct Tree{
#define lowbit(x) (x & -x)
static const int lim = maxn * 2;
int val[lim];
inline void insert(int pos, int dv){
    for(; pos < lim; pos += lowbit(pos))
        val[pos] += dv;
}
inline int query(int lim){
    int res = 0;
    for(; lim; lim -= lowbit(lim))
        res += val[lim];
    return res;
}
#undef lowbit
inline void clear(){
    memset(val, 0, sizeof(val));
}
}tree;
inline ll check(int lim){
//    cerr << "check " << lim << endl;
    ll res = 0;
    tree.clear();
    int base = n + 1;
    tree.insert(base, 1);
    for(int i = 0; i < n; ++i){
        base += a[i] >= lim? 1: -1;
        res += tree.query(base - 1);
        tree.insert(base, 1);
    }
//    cerr << "res: " << res << " intervals" << endl;
    return res;
}
#define READFILE
int main(){
#if    defined(MAC_OS_VERSION_11_0) && defined(READFILE)
    freopen("/Users/m2/Downloads/problem_2380/ex_median2.in", "r", stdin);
#endif
    cin.tie(0)->sync_with_stdio(false);
    cin >> n;
    for(int i = 0; i < n; ++i){
        cin >> a[i];
        vs[i] = a[i];
    }
    sort(vs, vs + n);
    vl = int(unique(vs, vs + n) - vs);
    for(int i = 0; i < n; ++i)
        a[i] = int(lower_bound(vs, vs + vl, a[i]) - vs);
//    cerr << "a = { ";
//    for(int i = 0; i < n; ++i)
//        cerr << a[i] << ' ';
//    cerr << "}" << endl;
    int lt = 0, rt = vl, mid;
    ll rank = ((ll(n + 1) * n / 2) + 1) / 2;
    while(lt < rt - 1){
        mid = (lt + rt) >> 1;
        if(check(mid) >= rank)
            lt = mid;
        else
            rt = mid;
    }
    cout << vs[lt] << endl;
    return 0;
}

Details

小提示:点击横条可展开更详细的信息

Test #1:

score: 10
Accepted
time: 0ms
memory: 3616kb

input:

200
247837946 222748444 549404903 934970141 181690491 116150147 755881953 912914845 578004877 589768...

output:

411892743

result:

ok 1 number(s): "411892743"

Test #2:

score: 10
Accepted
time: 0ms
memory: 3616kb

input:

200
504553675 321343511 781936447 172776833 779139954 643752948 106 164 303976944 828799931 11502170...

output:

451369372

result:

ok 1 number(s): "451369372"

Test #3:

score: 10
Accepted
time: 0ms
memory: 3616kb

input:

200
738368650 91602659 340556191 835209882 409442204 656938221 258295858 90658347 126689369 56196859...

output:

420852999

result:

ok 1 number(s): "420852999"

Test #4:

score: 10
Accepted
time: 6ms
memory: 3656kb

input:

5000
300051244 685920750 122806687 315801142 33592358 339985437 262520930 380010194 687330910 550362...

output:

465193387

result:

ok 1 number(s): "465193387"

Test #5:

score: 10
Accepted
time: 6ms
memory: 3660kb

input:

5000
108135249 950186870 146626753 682580494 744412491 4159 995071655 157947560 668940645 878891308 ...

output:

466892796

result:

ok 1 number(s): "466892796"

Test #6:

score: 10
Accepted
time: 6ms
memory: 3660kb

input:

5000
246610103 780664789 678774940 716124165 518453378 300121008 135383319 939869983 430946660 13412...

output:

470507384

result:

ok 1 number(s): "470507384"

Test #7:

score: 10
Accepted
time: 259ms
memory: 5960kb

input:

300000
786856547 380253059 684225515 795392038 881780483 18437791 793783577 832330260 801624996 3466...

output:

463539280

result:

ok 1 number(s): "463539280"

Test #8:

score: 10
Accepted
time: 263ms
memory: 5956kb

input:

300000
951000485 930070933 3566360 157114366 150196488 611226665 123590886 950624066 472150346 57976...

output:

462334620

result:

ok 1 number(s): "462334620"

Test #9:

score: 10
Accepted
time: 270ms
memory: 5956kb

input:

300000
728509094 406128756 696166390 756254976 31403187 672131182 35544213 870708756 3659210 5227553...

output:

464162969

result:

ok 1 number(s): "464162969"

Test #10:

score: 10
Accepted
time: 259ms
memory: 5956kb

input:

300000
804874490 52247250 546638789 400214210 383796618 47995083 814777769 507157584 466189162 28296...

output:

463577194

result:

ok 1 number(s): "463577194"

Extra Test:

score: 0
Extra Test Passed