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/**
* Author : Mr_Sohel
* Task :
* Algo :
**/
#include <bits/stdc++.h>
#define endl '\n'
#define sqr(x) (x) * (x)
#define gcd(x,y) __gcd(x,y)
#define lcm(x,y) ((x/gcd(x,y)) * y)
#define pb push_back
#define pf push_front
#define mk make_pair
#define fi first
#define se second
#define sz(x) (int)x.size()
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define prec(x) fixed<<setprecision(x)
#define min3(a,b,c) min(a,min(b,c))
#define max3(a,b,c) max(a,max(b,c))
#define min4(a,b,c,d) min(a,min(b,min(c,d)))
#define max4(a,b,c,d) max(a,max(b,max(c,d)))
#define unsyncIO ios_base::sync_with_stdio(false); cin.tie(nullptr)
using namespace std;
using ll = long long;
using db = double;
using ld = long double;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const ld PI = acos((ld) - 1);
const int MOD = 1e9 + 7;
const ll INF = 2e18 + 1;
const ld EPS = 1e-9;
const int MX = 1e5 + 5;
#ifdef LOCAL
#define debug(...) __f(#__VA_ARGS__, __VA_ARGS__)
template < typename Arg1 >
void __f(const char* name, Arg1&& arg1) {
cerr << name << " = " << arg1 << endl;
}
template < typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args) {
const char* comma = strchr(names + 1, ',');
cerr.write(names, comma - names) << " = " << arg1 << " | ";
__f(comma + 1, args...);
}
#else
#define debug(...)
#endif
ll n, c;
int a[MX];
bool check(ll mid) {
int cnt = 1, st = 0;
for (int i = 0; i < n; i++) {
if ((a[i + 1] - a[st]) >= mid) {
cnt++;
st = i + 1;
}
}
// debug(cnt);
return cnt >= c;
}
int main() {
#ifdef LOCAL
clock_t tStart = clock();
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif
unsyncIO;
int t; cin >> t;
while (t--) {
cin >> n >> c;
for (int i = 0; i < n; i++) cin >> a[i];
sort(a, a + n);
ll lo = 1, hi = 1e18, mid, ans;
while (lo <= hi) {
mid = lo + ((hi - lo) / 2);
// debug(mid);
if (check(mid)) {
lo = mid + 1;
ans = mid;
} else {
hi = mid - 1;
}
}
cout << ans << endl;
}
#ifdef LOCAL
cerr << "\nRuntime: " << (ld) (clock() - tStart) / CLOCKS_PER_SEC << " Seconds" << endl;
#endif
return 0;
} |