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+/******************************************************************************************[Heap.h]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#ifndef BasicHeap_h
+#define BasicHeap_h
+
+#include "Vec.h"
+
+//=================================================================================================
+// A heap implementation with support for decrease/increase key.
+
+
+template<class Comp>
+class BasicHeap {
+    Comp     lt;
+    vec<int> heap;     // heap of ints
+
+    // Index "traversal" functions
+    static inline int left  (int i) { return i*2+1; }
+    static inline int right (int i) { return (i+1)*2; }
+    static inline int parent(int i) { return (i-1) >> 1; }
+
+    inline void percolateUp(int i)
+    {
+        int x = heap[i];
+        while (i != 0 && lt(x, heap[parent(i)])){
+            heap[i]          = heap[parent(i)];
+            i                = parent(i);
+        }
+        heap   [i] = x;
+    }
+
+
+    inline void percolateDown(int i)
+    {
+        int x = heap[i];
+        while (left(i) < heap.size()){
+            int child = right(i) < heap.size() && lt(heap[right(i)], heap[left(i)]) ? right(i) : left(i);
+            if (!lt(heap[child], x)) break;
+            heap[i]          = heap[child];
+            i                = child;
+        }
+        heap[i] = x;
+    }
+
+
+    bool heapProperty(int i) {
+        return i >= heap.size()
+            || ((i == 0 || !lt(heap[i], heap[parent(i)])) && heapProperty(left(i)) && heapProperty(right(i))); }
+
+
+  public:
+    BasicHeap(const C& c) : comp(c) { }
+
+    int  size      ()                     const { return heap.size(); }
+    bool empty     ()                     const { return heap.size() == 0; }
+    int  operator[](int index)            const { return heap[index+1]; }
+    void clear     (bool dealloc = false)       { heap.clear(dealloc); }
+    void insert    (int n)                      { heap.push(n); percolateUp(heap.size()-1); }
+
+
+    int  removeMin() {
+        int r   = heap[0];
+        heap[0] = heap.last();
+        heap.pop();
+        if (heap.size() > 1) percolateDown(0);
+        return r; 
+    }
+
+
+    // DEBUG: consistency checking
+    bool heapProperty() {
+        return heapProperty(1); }
+
+
+    // COMPAT: should be removed
+    int  getmin    ()      { return removeMin(); }
+};
+
+
+//=================================================================================================
+#endif