AtCoder Regular Contest 203 (Div. 2)

Author: Macesuted

AtCoder/arc203_a.cpp

@@ -0,0 +1,42 @@
+/**
+ * @file arc203_a.cpp
+ * @author Macesuted (i@macesuted.moe)
+ * @date 2025-08-03
+ *
+ * @copyright Copyright (c) 2025
+ *
+ */
+
+#include <bits/stdc++.h>
+using namespace std;
+
+#ifndef LOCAL
+#define endl '\n'
+#endif
+
+bool mem1;
+
+void solve(void) {
+    int64_t n, m;
+    cin >> n >> m;
+    cout << n * (m / 2) + (m % 2) << endl;
+    return;
+}
+
+bool mem2;
+
+int main() {
+    ios::sync_with_stdio(false), cin.tie(nullptr);
+#ifdef LOCAL
+    cerr << "Memory Cost: " << abs(&mem1 - &mem2) / 1024. / 1024. << "MB" << endl;
+#endif
+
+    int _ = 1;
+    cin >> _;
+    while (_--) solve();
+
+#ifdef LOCAL
+    cerr << "Time Cost: " << clock() * 1000. / CLOCKS_PER_SEC << "MS" << endl;
+#endif
+    return 0;
+}

AtCoder/arc203_b.cpp

@@ -0,0 +1,53 @@
+/**
+ * @file arc203_b.cpp
+ * @author Macesuted (i@macesuted.moe)
+ * @date 2025-08-03
+ *
+ * @copyright Copyright (c) 2025
+ *
+ */
+
+#include <bits/stdc++.h>
+using namespace std;
+
+#ifndef LOCAL
+#define endl '\n'
+#endif
+
+bool mem1;
+
+#define maxn 200005
+
+int a[maxn], b[maxn];
+
+void solve(void) {
+    int n, cnt[2][2] = {{0, 0}, {0, 0}};
+    cin >> n;
+    for (int i = 1; i <= n; i++) cin >> a[i], cnt[0][a[i]]++;
+    bool same = true;
+    for (int i = 1; i <= n; i++) cin >> b[i], cnt[1][b[i]]++, same &= (a[i] == b[i]);
+
+    if (same) return cout << "Yes" << endl, void();
+    if (cnt[0][1] != cnt[1][1]) return cout << "No" << endl, void();
+    if (cnt[0][1] == 1 && (a[1] == 1 || a[n] == 1 || b[1] == 1 || b[n] == 1)) return cout << "No" << endl, void();
+    cout << "Yes" << endl;
+    return;
+}
+
+bool mem2;
+
+int main() {
+    ios::sync_with_stdio(false), cin.tie(nullptr);
+#ifdef LOCAL
+    cerr << "Memory Cost: " << abs(&mem1 - &mem2) / 1024. / 1024. << "MB" << endl;
+#endif
+
+    int _ = 1;
+    cin >> _;
+    while (_--) solve();
+
+#ifdef LOCAL
+    cerr << "Time Cost: " << clock() * 1000. / CLOCKS_PER_SEC << "MS" << endl;
+#endif
+    return 0;
+}

AtCoder/arc203_c.cpp

@@ -0,0 +1,77 @@
+/**
+ * @file arc203_c.cpp
+ * @author Macesuted (i@macesuted.moe)
+ * @date 2025-08-03
+ *
+ * @copyright Copyright (c) 2025
+ *
+ */
+
+#include <bits/stdc++.h>
+using namespace std;
+
+#ifndef LOCAL
+#define endl '\n'
+#endif
+
+bool mem1;
+
+#define maxn 1000005
+#define mod 998244353
+
+int64_t qpow(int64_t a, int64_t x) {
+    int64_t ans = 1;
+    while (x) {
+        if (x & 1) ans = ans * a % mod;
+        a = a * a % mod, x >>= 1;
+    }
+    return ans;
+}
+int64_t inv(int64_t a) { return qpow(a, mod - 2); }
+
+int64_t fac[maxn], ifac[maxn];
+
+int64_t binom(int n, int m) { return 0 <= m && m <= n ? fac[n] * ifac[m] % mod * ifac[n - m] % mod : 0; }
+
+void solve(void) {
+    int64_t n, m, k;
+    cin >> n >> m >> k;
+
+    if (k < n + m - 2) return cout << 0 << endl, void();
+    if (k == n + m - 2) return cout << binom(n + m - 2, n - 1) << endl, void();
+    if (k == n + m - 1) return cout << binom(n + m - 2, n - 1) * 2 * (n - 1) % mod * (m - 1) % mod << endl, void();
+
+    int64_t v1 = 0;
+    if (n >= 3) v1 = (v1 + binom(n + m - 3, m) * (m - 1) % mod * (n - 2) - binom(n + m - 3, m + 1) * m % mod * (m - 1)) % mod;
+    if (m >= 3) v1 = (v1 + binom(n + m - 3, n) * (n - 1) % mod * (m - 2) - binom(n + m - 3, n + 1) * n % mod * (n - 1)) % mod;
+
+    int64_t v2 = (2 * (n - 1) * (m - 1) - 1) % mod * (n - 1) % mod * (m - 1) % mod * binom(n + m - 2, n - 1) % mod;
+    int64_t v3 = (n + m - 3) * binom(n + m - 4, n - 2) % mod;
+
+    cout << ((v1 + v2 - v3) % mod + mod) % mod << endl;
+
+    return;
+}
+
+bool mem2;
+
+int main() {
+    ios::sync_with_stdio(false), cin.tie(nullptr);
+#ifdef LOCAL
+    cerr << "Memory Cost: " << abs(&mem1 - &mem2) / 1024. / 1024. << "MB" << endl;
+#endif
+
+    fac[0] = ifac[0] = 1;
+    for (int i = 1; i < maxn; i++) fac[i] = fac[i - 1] * i % mod;
+    ifac[maxn - 1] = inv(fac[maxn - 1]);
+    for (int i = maxn - 2; i; i--) ifac[i] = ifac[i + 1] * (i + 1) % mod;
+
+    int _ = 1;
+    cin >> _;
+    while (_--) solve();
+
+#ifdef LOCAL
+    cerr << "Time Cost: " << clock() * 1000. / CLOCKS_PER_SEC << "MS" << endl;
+#endif
+    return 0;
+}

AtCoder/arc203_d.cpp

@@ -0,0 +1,74 @@
+/**
+ * @file arc203_d.cpp
+ * @author Macesuted (i@macesuted.moe)
+ * @date 2025-08-03
+ *
+ * @copyright Copyright (c) 2025
+ *
+ */
+
+#include <bits/stdc++.h>
+using namespace std;
+
+#ifndef LOCAL
+#define endl '\n'
+#endif
+
+bool mem1;
+
+#define maxn 200005
+
+int a[maxn];
+
+void solve(void) {
+    int n;
+    cin >> n;
+    set<int> S[2];
+    for (int i = 1; i <= n; i++) cin >> a[i], S[a[i]].insert(i);
+
+    int xcnt = 0;
+    auto calc = [&](int p) -> bool { return p < 1 || p + 2 > n ? 0 : a[p] && !a[p + 1] && !a[p + 2]; };
+    for (int i = 1; i <= n; i++) xcnt += calc(i);
+
+    auto query = [&](void) -> int {
+        if (S[0].empty()) return n;
+        if (S[1].empty()) return 2;
+
+        int x0 = xcnt, pl = *S[1].begin() - 1, pr = n - *S[1].rbegin();
+        if (pr >= 2) x0--;
+        if (a[1] && a[n] && !x0) return 2;
+        int ans = x0 * 3 + 1;
+        return min(2, pl) + ans + min(2, pr);
+    };
+
+    int q;
+    cin >> q;
+    while (q--) {
+        int x;
+        cin >> x;
+        S[a[x]].erase(x);
+        xcnt -= calc(x - 2) + calc(x - 1) + calc(x);
+        S[a[x] = !a[x]].insert(x);
+        xcnt += calc(x - 2) + calc(x - 1) + calc(x);
+
+        cout << query() << endl;
+    }
+    return;
+}
+
+bool mem2;
+
+int main() {
+    ios::sync_with_stdio(false), cin.tie(nullptr);
+#ifdef LOCAL
+    cerr << "Memory Cost: " << abs(&mem1 - &mem2) / 1024. / 1024. << "MB" << endl;
+#endif
+
+    int _ = 1;
+    while (_--) solve();
+
+#ifdef LOCAL
+    cerr << "Time Cost: " << clock() * 1000. / CLOCKS_PER_SEC << "MS" << endl;
+#endif
+    return 0;
+}