牛客网NOIP赛前集训营-提高组（第一场）A 中位数

中位数

思路：

二分答案

代码：

#pragma GCC optimize(2)

#pragma GCC optimize(3)

#pragma GCC optimize(4)

#include<bits/stdc++.h>

using namespace std;

#define fi first

#define se second

#define pi acos(-1.0)

#define LL long long

#define mp make_pair

#define pb push_back

#define ls rt<<1, l, m

#define rs rt<<1|1, m+1, r

#define ULL unsigned LL

#define pll pair<LL, LL>

#define pii pair<int, int>

#define piii pair<pii, int>

#define mem(a, b) memset(a, b, sizeof(a))

#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

#define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout);

//head

const int N = 1e5 + ;

int a[N], b[N], n, len;

bool check(int x) {

    for (int i = ; i <= n; i++) if(a[i] < x) b[i] = -; else b[i] = ;

    int mn = INT_MAX;

    for (int i = ; i <= n; i++) {

        b[i] += b[i-];

        if(i >= len) mn = min(mn, b[i-len]);

        if(i >= len && b[i] - mn > ) return true;

    }

    return false;

}

int main() {

    scanf("%d %d", &n, &len);

    for (int i = ; i <= n; i++) scanf("%d", &a[i]);

    LL l = , r = 1e9, m = l+r+ >> ;

    while(l < r) {

        if(check(m)) l = m;

        else r = m-;

        m = l+r+ >> ;

    }

    printf("%d\n", m);

    return ;

}

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