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