algorithms/binary_heap.cpp at master · PaulKovalov/algorithms · GitHub

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#include <iostream>
#include <queue>

using namespace std;

/**
 * Array based implementation of the binary heap
 * */

template <class T>
class BinHeap {
  vector<T> v;
  int heap_size;

 public:
  BinHeap() { heap_size = 0; }
  void add(T value) {

    ++heap_size;
    v.push_back(value);
    int i = heap_size - 1;
    int parent = (i - 1) / 2;

    while (i > 0 && v[parent] < v[i]) {
      // swap them
      swap(v[parent], v[i]);
      i = parent;
      parent = (i - 1) / 2;
    }
  }
  void heapify(int i) {
    int left_child;
    int right_child;
    int largest_child;

    while (true) {
      left_child = 2 * i + 1;
      right_child = 2 * i + 2;
      largest_child = i;

      if (left_child < heap_size && v[left_child] > v[largest_child]) {
        largest_child = left_child;
      }
      if (right_child < heap_size && v[right_child] > v[largest_child]) {
        largest_child = right_child;
      }
      if (largest_child == i) {
        break;
      }
      swap(v[i], v[largest_child]);
      i = largest_child;
    }
  }
  void print_heap() {
    for (int i = 0; i < heap_size; ++i) {
      cout << v[i] << " ";
    }
    cout << endl;
  }
};

int main() {
  BinHeap<int> binHeap;
  binHeap.add(1);
  binHeap.add(2);
  binHeap.add(3);
  binHeap.add(4);
  binHeap.add(5);

  binHeap.print_heap();
  return 0;
}