QOJ: The 2025 ICPC Asia Shanghai Regional Contest (Upsolving)

Author: Macesuted

QOJ/15314.cpp

@@ -0,0 +1,87 @@
+/**
+ * @file 15314.cpp
+ * @author Macesuted (i@macesuted.moe)
+ * @date 2025-12-09
+ *
+ * @copyright Copyright (c) 2025
+ *
+ */
+
+#include <bits/stdc++.h>
+using namespace std;
+
+#define maxn 30005
+
+vector<vector<int>> graph;
+int dfni[maxn], dfno[maxn], fa[maxn], dep[maxn], sum[maxn];
+
+bool query(int p, int d) {
+    cout << "? " << p << ' ' << d << endl;
+    int ret;
+    cin >> ret;
+    return ret;
+}
+
+int dfnt;
+void dfs1(int p) {
+    dfni[p] = ++dfnt;
+    for (auto q : graph[p]) dep[q] = dep[p] + 1, dfs1(q);
+    dfno[p] = dfnt;
+    return;
+}
+
+void solve(void) {
+    int n;
+    cin >> n;
+    graph.clear(), graph.resize(n + 1);
+
+    for (int i = 2; i <= n; i++) cin >> fa[i], graph[fa[i]].push_back(i);
+    dfs1(1);
+
+    int l = 0, r = 0;
+    for (int i = 1; i <= n; i++) r = max(r, dep[i]);
+    while (l < r) {
+        int mid = (l + r) >> 1;
+        query(1, mid) ? (r = mid) : (l = mid + 1);
+    }
+
+    vector<int> rec;
+    for (int i = 1; i <= n; i++)
+        if (dep[i] == l) rec.push_back(i);
+
+    while (rec.size() > 1) {
+        for (int i = 1; i <= n; i++) sum[i] = 0;
+        for (auto p : rec) sum[p] = 1;
+        for (int i = n; i >= 1; i--)
+            for (auto j : graph[i]) sum[i] += sum[j];
+
+        int xp = -1, v = 0;
+        for (int i = 2; i <= n; i++)
+            if (v < min(sum[i], sum[1] - sum[i])) v = min(sum[i], sum[1] - sum[i]), xp = i;
+
+        vector<int> rd, ru;
+        for (auto p : rec)
+            if (dfni[xp] <= dfni[p] && dfni[p] <= dfno[xp])
+                rd.push_back(p);
+            else
+                ru.push_back(p);
+
+        int x = rd.front();
+        int ret = query(x, 2 * (dep[x] - dep[xp]));
+        rec = ret ? rd : ru;
+    }
+
+    cout << "! " << rec.front() << endl;
+
+    return;
+}
+
+int main() {
+    ios::sync_with_stdio(false), cin.tie(nullptr);
+
+    int _ = 1;
+    cin >> _;
+    while (_--) solve();
+
+    return 0;
+}

QOJ/15315.cpp

@@ -0,0 +1,80 @@
+/**
+ * @file 15315.cpp
+ * @author Macesuted (i@macesuted.moe)
+ * @date 2025-12-09
+ *
+ * @copyright Copyright (c) 2025
+ *
+ */
+
+#include <bits/stdc++.h>
+using namespace std;
+
+#define endl '\n'
+
+#define maxn 200005
+
+vector<vector<int>> graph;
+int a[maxn], dep[maxn], fa[maxn];
+bool vis[maxn];
+
+vector<int> ans;
+int sum;
+void dfs(int p) {
+    ans.push_back(p), a[p] ^= 1;
+    vis[p] = true;
+    for (auto q : graph[p]) {
+        if (vis[q]) {
+            if (sum && dep[q] <= dep[p] && !((dep[p] - dep[q]) & 1)) {
+                sum = 0;
+                int x = p;
+                while (x != q) ans.push_back(x = fa[x]), a[x] ^= 1;
+                ans.push_back(p), a[p] ^= 1;
+            }
+            continue;
+        }
+        dep[q] = dep[p] + 1, fa[q] = p, dfs(q);
+        ans.push_back(p), a[p] ^= 1;
+        if (a[q]) {
+            ans.push_back(q), a[q] ^= 1;
+            ans.push_back(p), a[p] ^= 1;
+        }
+    }
+    return;
+}
+
+void solve(void) {
+    int n, m, r;
+    cin >> n >> m >> r;
+
+    for (int i = 1; i <= n; i++) cin >> a[i], a[i] &= 1;
+
+    graph.clear(), graph.resize(n + 1);
+    for (int i = 1, x, y; i <= m; i++) cin >> x >> y, graph[x].push_back(y), graph[y].push_back(x);
+
+    ans.clear(), sum = 0;
+    for (int i = 1; i <= n; i++) sum ^= a[i], vis[i] = false;
+    a[r] ^= 1, dep[r] = 0, dfs(r);
+
+    for (int i = 1; i <= n; i++)
+        if (a[i]) return cout << "No" << endl, void();
+
+    ans.pop_back();
+    reverse(ans.begin(), ans.end());
+
+    cout << "Yes" << endl << ans.size() << endl;
+    for (auto x : ans) cout << x << ' ';
+    cout << endl;
+
+    return;
+}
+
+int main() {
+    ios::sync_with_stdio(false), cin.tie(nullptr);
+
+    int _ = 1;
+    cin >> _;
+    while (_--) solve();
+
+    return 0;
+}