1 | //===- llvm/ADT/PriorityQueue.h - Priority queues ---------------*- C++ -*-===// |
2 | // |
3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
4 | // See https://llvm.org/LICENSE.txt for license information. |
5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
6 | // |
7 | //===----------------------------------------------------------------------===// |
8 | /// |
9 | /// \file |
10 | /// This file defines the PriorityQueue class. |
11 | /// |
12 | //===----------------------------------------------------------------------===// |
13 | |
14 | #ifndef LLVM_ADT_PRIORITYQUEUE_H |
15 | #define LLVM_ADT_PRIORITYQUEUE_H |
16 | |
17 | #include <algorithm> |
18 | #include <queue> |
19 | |
20 | namespace llvm { |
21 | |
22 | /// PriorityQueue - This class behaves like std::priority_queue and |
23 | /// provides a few additional convenience functions. |
24 | /// |
25 | template<class T, |
26 | class Sequence = std::vector<T>, |
27 | class Compare = std::less<typename Sequence::value_type> > |
28 | class PriorityQueue : public std::priority_queue<T, Sequence, Compare> { |
29 | public: |
30 | explicit PriorityQueue(const Compare &compare = Compare(), |
31 | const Sequence &sequence = Sequence()) |
32 | : std::priority_queue<T, Sequence, Compare>(compare, sequence) |
33 | {} |
34 | |
35 | template<class Iterator> |
36 | PriorityQueue(Iterator begin, Iterator end, |
37 | const Compare &compare = Compare(), |
38 | const Sequence &sequence = Sequence()) |
39 | : std::priority_queue<T, Sequence, Compare>(begin, end, compare, sequence) |
40 | {} |
41 | |
42 | /// erase_one - Erase one element from the queue, regardless of its |
43 | /// position. This operation performs a linear search to find an element |
44 | /// equal to t, but then uses all logarithmic-time algorithms to do |
45 | /// the erase operation. |
46 | /// |
47 | void erase_one(const T &t) { |
48 | // Linear-search to find the element. |
49 | typename Sequence::size_type i = find(this->c, t) - this->c.begin(); |
50 | |
51 | // Logarithmic-time heap bubble-up. |
52 | while (i != 0) { |
53 | typename Sequence::size_type parent = (i - 1) / 2; |
54 | this->c[i] = this->c[parent]; |
55 | i = parent; |
56 | } |
57 | |
58 | // The element we want to remove is now at the root, so we can use |
59 | // priority_queue's plain pop to remove it. |
60 | this->pop(); |
61 | } |
62 | |
63 | /// reheapify - If an element in the queue has changed in a way that |
64 | /// affects its standing in the comparison function, the queue's |
65 | /// internal state becomes invalid. Calling reheapify() resets the |
66 | /// queue's state, making it valid again. This operation has time |
67 | /// complexity proportional to the number of elements in the queue, |
68 | /// so don't plan to use it a lot. |
69 | /// |
70 | void reheapify() { |
71 | std::make_heap(this->c.begin(), this->c.end(), this->comp); |
72 | } |
73 | |
74 | /// clear - Erase all elements from the queue. |
75 | /// |
76 | void clear() { |
77 | this->c.clear(); |
78 | } |
79 | }; |
80 | |
81 | } // End llvm namespace |
82 | |
83 | #endif |
84 | |