80 lines
2.0 KiB
C++
80 lines
2.0 KiB
C++
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#include <iostream>
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#include <deque>
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#include <cstring>
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#include <algorithm>
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using namespace std;
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const int N = 1000005;
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int arr[N], brr[N], crr[N], n;
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bool calc(char op) {
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deque<int> a, b;
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string out, append;
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out.push_back(op);
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append.push_back('L');
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if (op == 'L') {
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for (int i = 2; i < crr[1]; i++) a.push_back(i);
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for (int i = n; i > crr[1]; i--) b.push_back(i);
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} else {
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for (int i = 1; i < crr[n]; i++) a.push_back(i);
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for (int i = n - 1; i > crr[n]; i--) b.push_back(i);
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}
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while (!a.empty() || !b.empty()) {
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int x1 = !a.empty() ? a.front() : 0;
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int x2 = !b.empty() ? b.front() : 0;
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int y1 = !a.empty() ? a.back() : 0;
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int y2 = !b.empty() ? b.back() : 0;
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if (crr[x1] == y1) {
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out.push_back('L');
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append.push_back('L');
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a.pop_front();
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a.pop_back();
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} else if (crr[x1] == y2) {
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out.push_back('L');
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append.push_back('R');
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a.pop_front();
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b.pop_back();
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} else if (crr[x2] == y1) {
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out.push_back('R');
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append.push_back('L');
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b.pop_front();
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a.pop_back();
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} else if (crr[x2] == y2) {
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out.push_back('R');
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append.push_back('R');
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b.pop_front();
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b.pop_back();
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} else {
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return false;
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}
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}
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reverse(append.begin(), append.end());
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out += append;
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cout << out << endl;
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return true;
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}
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int main() {
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int T;
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cin >> T;
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while (T--) {
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cin >> n;
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memset(brr, 0, sizeof brr);
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n *= 2;
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crr[0] = -1;
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for (int i = 1; i <= n; i++) {
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cin >> arr[i];
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if (brr[arr[i]]) {
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crr[brr[arr[i]]] = i;
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crr[i] = brr[arr[i]];
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} else {
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brr[arr[i]] = i;
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}
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}
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if (!calc('L') && !calc('R')) cout << -1 << endl;
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}
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}
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