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binaryheap.hpp
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1 /* $Id: binaryheap.hpp 24900 2013-01-08 22:46:42Z planetmaker $ */
2
3 /*
4 * This file is part of OpenTTD.
5 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
6 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
7 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
8 */
9
12 #ifndef BINARYHEAP_HPP
13 #define BINARYHEAP_HPP
14
15 #include "../core/alloc_func.hpp"
16
18 #define BINARYHEAP_CHECK 0
19
20 #if BINARYHEAP_CHECK
21
22 #define CHECK_CONSISTY() this->CheckConsistency()
23 #else
24
25 #define CHECK_CONSISTY() ;
26 #endif
27
52 template <class T>
53 class CBinaryHeapT {
54 private:
55 uint items;
56 uint capacity;
57 T **data;
58
59 public:
64 explicit CBinaryHeapT(uint max_items)
65 : items(0)
66 , capacity(max_items)
67 {
68 this->data = MallocT<T *>(max_items + 1);
69 }
70
71 ~CBinaryHeapT()
72 {
73 this->Clear();
74 free(this->data);
75 this->data = NULL;
76 }
77
78 protected:
88 inline uint HeapifyDown(uint gap, T *item)
89 {
90 assert(gap != 0);
91
92 /* The first child of the gap is at [parent * 2] */
93 uint child = gap * 2;
94
95 /* while children are valid */
96 while (child <= this->items) {
97 /* choose the smaller child */
98 if (child < this->items && *this->data[child + 1] < *this->data[child]) {
99 child++;
100 }
101 /* is it smaller than our parent? */
102 if (!(*this->data[child] < *item)) {
103 /* the smaller child is still bigger or same as parent => we are done */
104 break;
105 }
106 /* if smaller child is smaller than parent, it will become new parent */
107 this->data[gap] = this->data[child];
108 gap = child;
109 /* where do we have our new children? */
110 child = gap * 2;
111 }
112 return gap;
113 }
114
124 inline uint HeapifyUp(uint gap, T *item)
125 {
126 assert(gap != 0);
127
128 uint parent;
129
130 while (gap > 1) {
131 /* compare [gap] with its parent */
132 parent = gap / 2;
133 if (!(*item < *this->data[parent])) {
134 /* we don't need to continue upstairs */
135 break;
136 }
137 this->data[gap] = this->data[parent];
138 gap = parent;
139 }
140 return gap;
141 }
142
143 #if BINARYHEAP_CHECK
144
145 inline void CheckConsistency()
146 {
147 for (uint child = 2; child <= this->items; child++) {
148 uint parent = child / 2;
149 assert(!(*this->data[child] < *this->data[parent]));
150 }
151 }
152 #endif
153
154 public:
160 inline uint Length() const { return this->items; }
161
167 inline bool IsEmpty() const { return this->items == 0; }
168
174 inline bool IsFull() const { return this->items >= this->capacity; }
175
181 inline T *Begin()
182 {
183 assert(!this->IsEmpty());
184 return this->data[1];
185 }
186
194 inline T *End()
195 {
196 return this->data[1 + this->items];
197 }
198
204 inline void Include(T *new_item)
205 {
206 if (this->IsFull()) {
207 assert(this->capacity < UINT_MAX / 2);
208
209 this->capacity *= 2;
210 this->data = ReallocT<T*>(this->data, this->capacity + 1);
211 }
212
213 /* Make place for new item. A gap is now at the end of the tree. */
214 uint gap = this->HeapifyUp(++items, new_item);
215 this->data[gap] = new_item;
216 CHECK_CONSISTY();
217 }
218
225 inline T *Shift()
226 {
227 assert(!this->IsEmpty());
228
229 T *first = this->Begin();
230
231 this->items--;
232 /* at index 1 we have a gap now */
233 T *last = this->End();
234 uint gap = this->HeapifyDown(1, last);
235 /* move last item to the proper place */
236 if (!this->IsEmpty()) this->data[gap] = last;
237
238 CHECK_CONSISTY();
239 return first;
240 }
241
247 inline void Remove(uint index)
248 {
249 if (index < this->items) {
250 assert(index != 0);
251 this->items--;
252 /* at position index we have a gap now */
253
254 T *last = this->End();
255 /* Fix binary tree up and downwards */
256 uint gap = this->HeapifyUp(index, last);
257 gap = this->HeapifyDown(gap, last);
258 /* move last item to the proper place */
259 if (!this->IsEmpty()) this->data[gap] = last;
260 } else {
261 assert(index == this->items);
262 this->items--;
263 }
264 CHECK_CONSISTY();
265 }
266
275 inline uint FindIndex(const T &item) const
276 {
277 if (this->IsEmpty()) return 0;
278 for (T **ppI = this->data + 1, **ppLast = ppI + this->items; ppI <= ppLast; ppI++) {
279 if (*ppI == &item) {
280 return ppI - this->data;
281 }
282 }
283 return 0;
284 }
285
290 inline void Clear() { this->items = 0; }
291 };
292
293 #endif /* BINARYHEAP_HPP */