Submission #315327

#	Time	Username	Problem	Language	Result	Execution time	Memory
315327		Kevin_Zhang_TW	Cat (info1cup19_cat)	C++17	0 / 100	1091 ms	384 KiB

cat

#include<bits/stdc++.h>
#define pb emplace_back
#define AI(i) begin(i), end(i)
using namespace std;
using ll = long long;
#ifdef KEV
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void kout() {cerr << endl;}
template<class T1, class ...T2>
void kout (T1 v, T2 ...e) { cerr << v << ' ', kout(e...); }
template<class T>
void debug(T L, T R) { while (L != R) cerr << *L << " \n"[next(L)==R], ++L; }
#else
#define DE(...) 0
#define debug(...) 0
#endif
const int MAX_N = 300010;
int n;
vector<pair<int,int>> op;
// just the front half
void swap_sort(vector<int> p) {
}
bool valid(vector<int> p) {
	int cnt = 0, m = n / 2;
	for (int l = 0, r = n-1;l < r;++l, --r) {
		if ((p[l]>m) ^ (p[r]<=m))
			return false;
		if (p[l] > m)
			++cnt;
	}
	if (cnt & 1) 
		return false;
	vector<int> pos(n);
	for (int i = 0;i < n;++i)
		pos[ p[i] ] = i;
	auto sw = [&](int x, int y) {
		swap(p[x], p[y]), swap(pos[ p[x] ], pos[ p[y] ]);
	};
	auto do_op = [&](int x, int y) {
		int a = x, b = y, c = n - x - 1, d = n - y - 1;
		sw(a, b), sw(c, d);
	};
	for (int i = 0;i < m;++i) {
		while (i+1 != p[i]) 
			do_op(i, p[i]);
	}
	for (int i = 0;i < n;++i)
		if (p[i] != i+1)
			return false;
	return true;
}
// make p good enough so that I can do swap sort on it
void pair_good(vector<int> &p) {
}
bool solve() {
	cin >> n;
	vector<int> p(n);
	for (int &i : p)
		cin >> i;
	if (!valid(p))
		return false;
	pair_good(p);
	swap_sort(p);
	return true;
}
signed main() {
	ios_base::sync_with_stdio(0), cin.tie(0);
	int T;
	cin >> T;
	while (T--) {
		op.clear();
		if (!solve())
			cout << -1 << '\n';
		else {
			cout << op.size() << ' ' << op.size() << '\n';
			for (auto [a, b] : op)
				cout << a+1 << ' ' << b+1 << '\n';
		}
	}
}

• Subtask 1: 0 / 15
• Subtask 2: 0 / 10
• Subtask 3: 0 / 25
• Subtask 4: 0 / 15
• Subtask 5: 0 / 35