C++ 在序列上執行特定操作
假設我們給定一個空序列和 n 個查詢,我們需要處理這些查詢。這些查詢以陣列查詢形式給出,並採用 {查詢,資料} 的格式。查詢可以是以下三種類型之一:
query = 1:將提供的資料新增到序列末尾。
query = 2:列印序列開頭元素。之後刪除元素。
query = 3:按升序對序列進行排序。
請注意,查詢型別 2 和 3 始終具有資料 = 0。
因此,如果輸入為 n = 9,查詢 = {{1, 5}, {1, 4}, {1, 3}, {1, 2}, {1, 1}, {2, 0}, {3, 0}, {2, 0}, {3, 0}},則輸出為 5 和 1。
每個查詢後的序列如下所示:
- 1: {5}
- 2: {5, 4}
- 3: {5, 4, 3}
- 4: {5, 4, 3, 2}
- 5: {5, 4, 3, 2, 1}
- 6: {4, 3, 2, 1},列印 5。
- 7: {1, 2, 3, 4}
- 8: {2, 3, 4},列印 1。
- 9: {2, 3, 4}
為解決這個問題,我們將遵循以下步驟:
priority_queue<int> priq Define one queue q for initialize i := 0, when i < n, update (increase i by 1), do: operation := first value of queries[i] if operation is same as 1, then: x := second value of queries[i] insert x into q otherwise when operation is same as 2, then: if priq is empty, then: print first element of q delete first element from q else: print -(top element of priq) delete top element from priq otherwise when operation is same as 3, then: while (not q is empty), do: insert (-first element of q) into priq and sort delete element from q
示例
讓我們看看以下實現,以獲得更好的理解:
#include <bits/stdc++.h> using namespace std; void solve(int n, vector<pair<int, int>> queries){ priority_queue<int> priq; queue<int> q; for(int i = 0; i < n; i++) { int operation = queries[i].first; if(operation == 1) { int x; x = queries[i].second; q.push(x); } else if(operation == 2) { if(priq.empty()) { cout << q.front() << endl; q.pop(); } else { cout << -priq.top() << endl; priq.pop(); } } else if(operation == 3) { while(!q.empty()) { priq.push(-q.front()); q.pop(); } } } } int main() { int n = 9; vector<pair<int, int>> queries = {{1, 5}, {1, 4}, {1, 3}, {1, 2}, {1, 1}, {2, 0}, {3, 0}, {2, 0}, {3, 0}}; solve(n, queries); return 0; }
輸入
9, {{1, 5}, {1, 4}, {1, 3}, {1, 2}, {1, 1}, {2, 0}, {3, 0}, {2, 0}, {3, 0}}
輸出
5 1
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