题解

#include <bits/stdc++.h>

using namespace std;

int main() {
	int n, k;
	cin >> n >> k;
	int ar[n];

	for (int i = 0; i < n; i++) { cin >> ar[i]; }

	sort(ar, ar + n);

	int lo = 1, hi = 1e9;
	int sol = 1e9;

	while (lo <= hi) {
		int mid = lo + (hi - lo) / 2;
		int i = 0;
		for (int kas = 0; kas < k && i < n; kas++) {
			int hasta = ar[i];
			hasta += mid * 2;
			while (i < n - 1 && ar[i + 1] <= hasta) i++;
			i++;
		}
		bool ok;
		ok = (i >= n);
		if (ok) {
			sol = min(sol, mid);
			hi = mid - 1;
		} else {
			lo = mid + 1;
		}
	}

	cout << sol << '\n';
}