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binaryheap.hpp
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1 /* $Id: binaryheap.hpp 27363 2015-08-08 13:19:38Z alberth $ */
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
161 {
162 return this->items;
163 }
164
170 inline bool IsEmpty() const
171 {
172 return this->items == 0;
173 }
174
180 inline bool IsFull() const
181 {
182 return this->items >= this->capacity;
183 }
184
190 inline T *Begin()
191 {
192 assert(!this->IsEmpty());
193 return this->data[1];
194 }
195
203 inline T *End()
204 {
205 return this->data[1 + this->items];
206 }
207
213 inline void Include(T *new_item)
214 {
215 if (this->IsFull()) {
216 assert(this->capacity < UINT_MAX / 2);
217
218 this->capacity *= 2;
219 this->data = ReallocT<T*>(this->data, this->capacity + 1);
220 }
221
222 /* Make place for new item. A gap is now at the end of the tree. */
223 uint gap = this->HeapifyUp(++items, new_item);
224 this->data[gap] = new_item;
225 CHECK_CONSISTY();
226 }
227
234 inline T *Shift()
235 {
236 assert(!this->IsEmpty());
237
238 T *first = this->Begin();
239
240 this->items--;
241 /* at index 1 we have a gap now */
242 T *last = this->End();
243 uint gap = this->HeapifyDown(1, last);
244 /* move last item to the proper place */
245 if (!this->IsEmpty()) this->data[gap] = last;
246
247 CHECK_CONSISTY();
248 return first;
249 }
250
256 inline void Remove(uint index)
257 {
258 if (index < this->items) {
259 assert(index != 0);
260 this->items--;
261 /* at position index we have a gap now */
262
263 T *last = this->End();
264 /* Fix binary tree up and downwards */
265 uint gap = this->HeapifyUp(index, last);
266 gap = this->HeapifyDown(gap, last);
267 /* move last item to the proper place */
268 if (!this->IsEmpty()) this->data[gap] = last;
269 } else {
270 assert(index == this->items);
271 this->items--;
272 }
273 CHECK_CONSISTY();
274 }
275
284 inline uint FindIndex(const T &item) const
285 {
286 if (this->IsEmpty()) return 0;
287 for (T **ppI = this->data + 1, **ppLast = ppI + this->items; ppI <= ppLast; ppI++) {
288 if (*ppI == &item) {
289 return ppI - this->data;
290 }
291 }
292 return 0;
293 }
294
299 inline void Clear()
300 {
301 this->items = 0;
302 }
303 };
304
305 #endif /* BINARYHEAP_HPP */