1 //===- llvm/ADT/PriorityQueue.h - Priority queues ---------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the PriorityQueue class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_ADT_PRIORITY_QUEUE_H
15 #define LLVM_ADT_PRIORITY_QUEUE_H
21 /// PriorityQueue - This class behaves like std::priority_queue and
22 /// provides a few additional convenience functions.
25 class Sequence = std::vector<T>,
26 class Compare = std::less<typename Sequence::value_type> >
27 class PriorityQueue : public std::priority_queue<T, Sequence, Compare> {
29 explicit PriorityQueue(const Compare &compare = Compare(),
30 const Sequence &sequence = Sequence())
31 : std::priority_queue<T, Sequence, Compare>(compare, sequence)
34 template<class Iterator>
35 PriorityQueue(Iterator begin, Iterator end,
36 const Compare &compare = Compare(),
37 const Sequence &sequence = Sequence())
38 : std::priority_queue<T, Sequence, Compare>(begin, end, compare, sequence)
41 /// erase_one - Erase one element from the queue, regardless of its
42 /// position. This operation performs a linear search to find an element
43 /// equal to t, but then uses all logarithmic-time algorithms to do
44 /// the erase operation.
46 void erase_one(const T &t) {
47 // Linear-search to find the element.
48 typename Sequence::size_type i =
49 std::find(this->c.begin(), this->c.end(), t) - this->c.begin();
51 // Logarithmic-time heap bubble-up.
53 typename Sequence::size_type parent = (i - 1) / 2;
54 this->c[i] = this->c[parent];
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.
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.
71 std::make_heap(this->c.begin(), this->c.end(), this->comp);
74 /// clear - Erase all elements from the queue.
81 } // End llvm namespace