More problems.

Teza Round 1 (Codeforces Round 1015, Div. 1 + Div. 2)/C. You Soared Afar With Grace.cpp

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+/* Problem URL: https://codeforces.com/problemset/problem/2084/C */
+
+#include <bits/stdc++.h>
+#include <ext/pb_ds/assoc_container.hpp>
+#include <ext/pb_ds/tree_policy.hpp>
+
+using namespace std;
+using namespace __gnu_pbds;
+
+template <class T, class comp = less<>>
+using ordered_set = tree<T, null_type , comp , rb_tree_tag , tree_order_statistics_node_update>;
+
+#define V vector
+
+#define rmin(a, b) a = min(a, b)
+#define rmax(a, b) a = max(a, b)
+
+#define rep(i, lim) for (int i = 0; i < (lim); i++)
+#define nrep(i, s, lim) for (int i = s; i < (lim); i++)
+
+#define repv(i, v) for (auto &i : (v))
+#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
+#define sortv(v) sort(v.begin(), v.end())
+#define all(v) (v).begin(), (v).end()
+
+using vi = vector<int>;
+using vvi = vector<vi>;
+using vvvi = vector<vvi>;
+using vvvvi = vector<vvvi>;
+
+using ll = long long;
+
+using vl = vector<ll>;
+using vvl = vector<vl>;
+using vvvl = vector<vvl>;
+using vvvvl = vector<vvvl>;
+
+template<class v>
+auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
+    os << vec[0];
+    for (size_t i = 1; i < vec.size(); i++) {
+        os << ' ' << vec[i];
+    }
+    os << '\n';
+    return os;
+}
+
+template<class v>
+auto operator>>(istream &is, vector<v> &vec)->istream& {
+    for (auto &i : vec) {
+        is >> i;
+    }
+    return is;
+}
+
+template<class v>
+auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
+    for (auto &i : vec) {
+        os << i[0];
+        for (size_t j = 1; j < i.size(); j++) {
+            os << ' ' << i[j];
+        }
+        os << '\n';
+    }
+    return os;
+}
+
+template<class v>
+auto operator>>(istream  &is, vector<vector<v>> &vec)->istream& {
+    for (auto &i : vec) {
+        for (auto &j : i) {
+            is >> j;
+        }
+    }
+    return is;
+}
+
+const int oo = INT32_MAX >> 1;
+const ll OO = INT64_MAX >> 1;
+
+
+void pre()
+{
+
+}
+
+#define TEST 1
+
+void solve()
+{
+    int n;
+    cin >> n;
+    vi a(n);
+    vi b(n);
+    cin >> a >> b;
+
+    int c = 0;
+    int p;
+
+    map<pair<int, int>, int> s;
+    rep(i, n) {
+        s[{a[i], b[i]}] = i;
+        if (a[i] == b[i]) {
+            c++;
+            p = i;
+        }
+    }
+
+    if ((c > 0 && (~n & 1)) || (c != 1 && (n & 1))) {
+        cout << "-1\n";
+        return;
+    }
+
+    rep(i, n) {
+        if (!s.count({b[i], a[i]})) {
+            cout << "-1\n";
+            return;
+        }
+    }
+
+    V<pair<int, int>> ans;
+
+    if (c && p != (n >> 1)) {
+        ans.emplace_back(p + 1, (n >> 1) + 1);
+        swap(a[p], a[n >> 1]);
+        swap(b[p], b[n >> 1]);
+        swap(s[{a[p], b[p]}], s[{a[n >> 1], b[n >> 1]}]);
+    }
+
+    rep(i, n >> 1) {
+        int rev = n - i - 1;
+        auto itr = s.find({b[i], a[i]});
+
+        if (itr->second == rev) {
+            continue;
+        }
+
+        ans.emplace_back(itr->second + 1, rev + 1);
+        auto itr2 = s.find({a[rev], b[rev]});
+        swap(a[rev], a[itr->second]);
+        swap(b[rev], b[itr->second]);
+        swap(itr->second, itr2->second);
+    }
+
+    cout << ans.size() << '\n';
+    repv(i, ans) {
+        cout << i.first << ' ' << i.second << '\n';
+    }
+}
+
+int main()
+{
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    pre();
+
+    int t;
+    (TEST && cin >> t) || (t = 1);
+    while (t--) {
+        solve();
+    }
+}