feat(cf): update ignore

codeforces/971/e.cc

@@ -0,0 +1,53 @@
+#include <algorithm>
+#include <cmath>
+#include <iostream>
+
+using namespace std;
+#define ll long long
+
+using ld = long double;
+
+auto inclusive_sum = [](unsigned ll l, unsigned ll r) {
+  unsigned ll sum_r = r / 2 * (r + 1);
+  if (r % 2)
+    sum_r += (r + 1) / 2;
+  l--;
+  unsigned ll sum_l = l / 2 * (l + 1);
+  if (l % 2)
+    sum_l += (l + 1) / 2;
+  return sum_r - sum_l;
+};
+
+auto quad = [](ld a, ld b, ld c) {
+  return (-b + sqrt(b * b - 4 * a * c)) / (2 * a);
+};
+
+void solve() {
+  unsigned ll n, k;
+  cin >> n >> k;
+
+  ll half = inclusive_sum(k, k + n - 1) / 2;
+
+  ld i = quad(0.5, k + 0.5, -half);
+
+  unsigned ll a = max(1LL, static_cast<ll>(ceil(i)));
+  unsigned ll b = min(n, a + 1);
+
+  unsigned ll x = inclusive_sum(k, k + a - 1);
+  unsigned ll y = inclusive_sum(k + a, k + n - 1);
+  unsigned ll diff1 = x < y ? y - x : x - y;
+
+  x = inclusive_sum(k, k + b - 1);
+  y = inclusive_sum(k + b, k + n - 1);
+  unsigned ll diff2 = x < y ? y - x : x - y;
+
+  cout << min(diff1, diff2) << endl;
+}
+
+int main() {
+  int t;
+  cin >> t;
+  while (t--)
+    solve();
+  return 0;
+}