kuangbin带你飞 【二分】HDU 3579 Median（整数二分）

题意题解：待更新

///*题意：给定一个数列，计算树立里面每个数之间的差值的绝对值，形成一个新的数列，求这个数列的中位数*/
///*思路：*/
//
//
#include<cstdio>
#include<iostream>
#include<cstring>
#include<cmath>
#include<algorithm>
#define ll long long
#define int ll
#define INF 0x3f3f3f3f
#define maxn 100010
using namespace std;
int a[maxn];
int n, k;
void cal(int l, int r)
{
    
    
	if (l >= r) {
    
    
		printf("%lld\n", l);
		return;
	}
	int mid = l + r >> 1;
	int cnt = 0;
	for (int i = 1; i <= n; i++) {
    
    
		int t = upper_bound(a + 1, a + n + 1, a[i] + mid) - a;
		cnt += t - i - 1;
	}
	if (cnt >= k) cal(l, mid);
	else cal(mid + 1, r);
}
signed main()
{
    
    
	while (~scanf("%lld", &n)) {
    
    
		memset(a, 0, sizeof(a));
		for (int i = 1; i <= n; i++)
			scanf("%lld", &a[i]);
		k = (n * (n - 1) >> 1) + 1 >> 1;
		sort(a + 1, a + n + 1);
		cal(0, a[n] - a[1]);
	}
	return 0;
}