47 lines
1.1 KiB
C++
47 lines
1.1 KiB
C++
#include <iostream>
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#include <stack>
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#include <vector>
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using Operation = std::pair<bool, int>;
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int n, idx = 0;
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std::stack<int> stack;
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std::vector<int> sequence;
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std::vector<Operation> operation_log;
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int main() {
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std::ios::sync_with_stdio(false);
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std::cin.tie(nullptr);
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std::cin >> n;
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operation_log.reserve(2 * n);
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sequence.resize(n);
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for (int i = 0; i < n; i++) {
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std::cin >> sequence[i];
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}
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for (int current_num = 1; current_num <= n;) {
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while ((stack.empty() || stack.top() != sequence[idx]) && current_num <= n) {
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stack.push(current_num);
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operation_log.emplace_back(false, current_num);
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current_num++;
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}
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while (!stack.empty() && stack.top() == sequence[idx]) {
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stack.pop();
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operation_log.emplace_back(true, sequence[idx]);
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idx++;
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}
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}
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if (!stack.empty()) {
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std::cout << "NO" << std::endl;
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} else {
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for (const auto [op, x] : operation_log) {
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std::cout << (op ? "POP " : "PUSH ") << x << std::endl;
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}
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}
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return 0;
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}
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