forked from google/or-tools
-
Notifications
You must be signed in to change notification settings - Fork 9
/
adjustable_priority_queue.h
194 lines (168 loc) · 5.81 KB
/
adjustable_priority_queue.h
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
// Copyright 2010-2024 Google LLC
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef OR_TOOLS_BASE_ADJUSTABLE_PRIORITY_QUEUE_H_
#define OR_TOOLS_BASE_ADJUSTABLE_PRIORITY_QUEUE_H_
#include <stddef.h>
#include <functional>
#include <list>
#include <vector>
#include "ortools/base/macros.h"
template <typename T, typename Comparator>
class LowerPriorityThan {
public:
explicit LowerPriorityThan(Comparator* compare) : compare_(compare) {}
bool operator()(T* a, T* b) const { return (*compare_)(*a, *b); }
private:
Comparator* compare_;
};
template <typename T, typename Comp = std::less<T> >
class AdjustablePriorityQueue {
public:
// The objects references 'c' and 'm' are not required to be alive for the
// lifetime of this object.
AdjustablePriorityQueue() = default;
explicit AdjustablePriorityQueue(const Comp& c) : c_(c) {}
AdjustablePriorityQueue(const AdjustablePriorityQueue&) = delete;
AdjustablePriorityQueue& operator=(const AdjustablePriorityQueue&) = delete;
AdjustablePriorityQueue(AdjustablePriorityQueue&&) = default;
AdjustablePriorityQueue& operator=(AdjustablePriorityQueue&&) = default;
void Add(T* val) {
// Extend the size of the vector by one. We could just use
// vector<T>::resize(), but maybe T is not default-constructible.
elems_.push_back(val);
AdjustUpwards(elems_.size() - 1);
}
void Remove(T* val) {
int end = elems_.size() - 1;
int i = val->GetHeapIndex();
if (i == end) {
elems_.pop_back();
return;
}
elems_[i] = elems_[end];
elems_[i]->SetHeapIndex(i);
elems_.pop_back();
NoteChangedPriority(elems_[i]);
}
bool Contains(const T* val) const {
int i = val->GetHeapIndex();
return (i >= 0 && i < elems_.size() && elems_[i] == val);
}
void NoteChangedPriority(T* val) {
LowerPriorityThan<T, Comp> lower_priority(&c_);
int i = val->GetHeapIndex();
int parent = (i - 1) / 2;
if (lower_priority(elems_[parent], val)) {
AdjustUpwards(i);
} else {
AdjustDownwards(i);
}
}
// If val ever changes its priority, you need to call this function
// to notify the pq so it can move it in the heap accordingly.
T* Top() { return elems_[0]; }
const T* Top() const { return elems_[0]; }
void AllTop(std::vector<T*>* topvec) {
topvec->clear();
if (Size() == 0) return;
std::list<int> need_to_check_children;
need_to_check_children.push_back(0);
// Implements breadth-first search down tree, stopping whenever
// there's an element < top
while (!need_to_check_children.empty()) {
int ind = need_to_check_children.front();
need_to_check_children.pop_front();
topvec->push_back(elems_[ind]);
int leftchild = 1 + 2 * ind;
if (leftchild < Size()) {
if (!LowerPriorityThan<T, Comp>(&c_)(elems_[leftchild], elems_[ind])) {
need_to_check_children.push_back(leftchild);
}
int rightchild = leftchild + 1;
if (rightchild < Size() &&
!LowerPriorityThan<T, Comp>(&c_)(elems_[rightchild], elems_[ind])) {
need_to_check_children.push_back(rightchild);
}
}
}
}
// If there are ties for the top, this returns all of them.
void Pop() { Remove(Top()); }
int Size() const { return elems_.size(); }
// Returns the number of elements for which storage has been allocated.
int Capacity() const { return elems_.capacity(); }
// Allocates storage for a given number of elements.
void SetCapacity(size_t c) { elems_.reserve(c); }
bool IsEmpty() const { return elems_.empty(); }
void Clear() { elems_.clear(); }
// CHECKs that the heap is actually a heap (each "parent" of >=
// priority than its child).
void CheckValid() {
for (int i = 0; i < elems_.size(); ++i) {
int left_child = 1 + 2 * i;
if (left_child < elems_.size()) {
CHECK(
!(LowerPriorityThan<T, Comp>(&c_))(elems_[i], elems_[left_child]));
}
int right_child = left_child + 1;
if (right_child < elems_.size()) {
CHECK(
!(LowerPriorityThan<T, Comp>(&c_))(elems_[i], elems_[right_child]));
}
}
}
// This is for debugging, e.g. the caller can use it to
// examine the heap for rationality w.r.t. other parts of the
// program.
const std::vector<T*>* Raw() const { return &elems_; }
private:
void AdjustUpwards(int i) {
T* const t = elems_[i];
while (i > 0) {
const int parent = (i - 1) / 2;
if (!c_(*elems_[parent], *t)) {
break;
}
elems_[i] = elems_[parent];
elems_[i]->SetHeapIndex(i);
i = parent;
}
elems_[i] = t;
t->SetHeapIndex(i);
}
void AdjustDownwards(int i) {
T* const t = elems_[i];
while (true) {
const int left_child = 1 + 2 * i;
if (left_child >= elems_.size()) {
break;
}
const int right_child = left_child + 1;
const int next_i = (right_child < elems_.size() &&
c_(*elems_[left_child], *elems_[right_child]))
? right_child
: left_child;
if (!c_(*t, *elems_[next_i])) {
break;
}
elems_[i] = elems_[next_i];
elems_[i]->SetHeapIndex(i);
i = next_i;
}
elems_[i] = t;
t->SetHeapIndex(i);
}
Comp c_;
std::vector<T*> elems_;
};
#endif // OR_TOOLS_BASE_ADJUSTABLE_PRIORITY_QUEUE_H_