Add C++ Heap Sort using heap based on Vectors

Author: arvchristos

Sorting/Heapsort.cpp

@@ -0,0 +1,131 @@
+#include <iostream>
+#include <cstdio>
+#include <vector>
+#include <iostream>
+#include <climits>
+
+using namespace std; //Not the best tactic, used for cleaner code and better understanding
+
+class Heap {
+private:
+std::vector<int> heap;
+int hpsz;
+public:
+
+Heap(){
+        hpsz=0; //At first the Heap is Empty
+        heap.push_back(0);  //Index 0 must be initialized because we start indexing from 1
+}
+
+Heap(std::vector<int>& array){
+        int n = array.size();
+        heap.push_back(100);  //The first index of heap array is 1 so we must fill 0 index with dummy content let it be 0
+        heap.insert(heap.end(),array.begin(),array.end());  //προσθέτω το 0
+        hpsz=n; //Heap size = Heap Array size
+        for (int i = n / 2; i > 0; i--) combine(i);
+}
+
+void insert(int elmnt) {
+        heap.push_back(elmnt);
+        hpsz++;
+        int i = hpsz, parent = i / 2;
+        while ((i > 1) && (heap[parent] < heap[i]))
+        {
+                iter_swap(heap.begin() + parent, heap.begin() + i);
+                i = parent; parent = i / 2;
+        }
+}
+
+//Get max without deleting from heap
+int peek_max(){
+        return heap[1];
+}
+
+void combine (int i){
+        int mp=i,left=2*i,right=(2*i)+1;
+        if((left<=hpsz) && (heap[left]>heap[mp])) {
+                mp = left;
+        }
+        if((right<=hpsz) && (heap[right]>heap[mp])) {
+                mp = right;
+        }
+        if(mp!=i) {
+                iter_swap(heap.begin() + i, heap.begin() + mp);
+                combine(mp);
+        }
+}
+
+int deletemax(){
+        if(isEmpty()) return -1;
+        int max = heap[1];
+
+        heap[1] = heap[hpsz--];
+        combine(1);
+        return max;
+}
+
+bool isEmpty(){
+        return (hpsz==0);
+}
+
+int getHeapSize(){
+        return (hpsz);
+}
+
+void heapSort(){
+        int temp = hpsz;
+        for (int i = hpsz; i > 1; i--)  {
+                iter_swap(heap.begin() + 1, heap.begin() + i);
+                hpsz--;
+                combine(1);
+        }
+        hpsz = temp;
+}
+
+void printHeap(){
+        for (int i = 1; i <= hpsz; i++) {
+                printf("%d ", heap[i] );
+        }
+        printf("\n");
+}
+};
+
+int main(){
+        /*
+           Heap can be constructed using vector as input
+         */
+        int a[] = {3,4,10,8,15,16,17,12,11,20};
+        vector<int> heapin (a, a + sizeof(a) / sizeof(a[0]) ); //C++2003
+        //std::vector<int> heapin ({3,4,10,8,15,16,17,12,11,20}); //C++2011
+        // std::vector<int> heapin(std::begin(a), std::end(a));    //C++2003
+        Heap test(heapin);
+        /*
+           Heap can be constructed using one by one insertion of elements
+           <-------------------------------------------------------------->
+           Heap test;
+           int num_elements;
+           printf("Enter number of elements\n");
+           scanf("%d\n",&num_elements);
+           int elem;
+
+           while(num_elements!=0) {
+                  num_elements--;
+                  scanf("%dendl",&elem );
+                  test.insert(elem);
+           }
+         */
+
+        test.printHeap(); //Heap array
+        test.heapSort();  //after heap sorting the array does not include a list
+        test.printHeap(); //Sorted array
+
+        /*
+         * Use the following loop to extract all the elements from head of max heap
+           while (!test.isEmpty()) {
+                printf("Max after delete: %d\n", test.deletemax());
+           }
+         */
+
+
+
+}