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 ;
}