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//===- llvm/ADT/PriorityQueue.h - Priority queues ---------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the PriorityQueue class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_PRIORITYQUEUE_H
#define LLVM_ADT_PRIORITYQUEUE_H
#include <algorithm>
#include <queue>
namespace llvm {
/// PriorityQueue - This class behaves like std::priority_queue and
/// provides a few additional convenience functions.
///
template<class T,
class Sequence = std::vector<T>,
class Compare = std::less<typename Sequence::value_type> >
class PriorityQueue : public std::priority_queue<T, Sequence, Compare> {
public:
explicit PriorityQueue(const Compare &compare = Compare(),
const Sequence &sequence = Sequence())
: std::priority_queue<T, Sequence, Compare>(compare, sequence)
{}
template<class Iterator>
PriorityQueue(Iterator begin, Iterator end,
const Compare &compare = Compare(),
const Sequence &sequence = Sequence())
: std::priority_queue<T, Sequence, Compare>(begin, end, compare, sequence)
{}
/// erase_one - Erase one element from the queue, regardless of its
/// position. This operation performs a linear search to find an element
/// equal to t, but then uses all logarithmic-time algorithms to do
/// the erase operation.
///
void erase_one(const T &t) {
// Linear-search to find the element.
typename Sequence::size_type i = find(this->c, t) - this->c.begin();
// Logarithmic-time heap bubble-up.
while (i != 0) {
typename Sequence::size_type parent = (i - 1) / 2;
this->c[i] = this->c[parent];
i = parent;
}
// The element we want to remove is now at the root, so we can use
// priority_queue's plain pop to remove it.
this->pop();
}
/// reheapify - If an element in the queue has changed in a way that
/// affects its standing in the comparison function, the queue's
/// internal state becomes invalid. Calling reheapify() resets the
/// queue's state, making it valid again. This operation has time
/// complexity proportional to the number of elements in the queue,
/// so don't plan to use it a lot.
///
void reheapify() {
std::make_heap(this->c.begin(), this->c.end(), this->comp);
}
/// clear - Erase all elements from the queue.
///
void clear() {
this->c.clear();
}
};
} // End llvm namespace
#endif
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