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Author: skjha1

Heap/01 InsertinHeap.cpp

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+#include <iostream>
+#include <vector>
+
+using namespace std;
+ 
+// Lecture based
+void InsertA(int A[], int n){
+    int i = n;
+    int temp = A[n];
+    while (i > 0 && temp > A[i % 2 == 0 ? (i/2)-1 : i/2]){
+        A[i] = A[i % 2 == 0 ? (i/2)-1 : i/2];
+        i = i % 2 == 0 ? (i/2)-1 : i/2;
+    }
+    A[i] = temp;
+}
+ 
+ 
+// STL vector based
+void Insert(vector<int>& vec, int key){
+    // Insert key at the end
+    auto i = vec.size();
+    vec.emplace_back(key);
+ 
+    // Rearrange elements: Indices are not DRY :-(
+    while (i > 0 && key > vec[i % 2 == 0 ? (i/2)-1 : i/2]){
+        vec[i] = vec[i % 2 == 0 ? (i/2)-1 : i/2];
+        i = i % 2 == 0 ? (i/2)-1 : i/2;
+    }
+    vec[i] = key;
+}
+ 
+template <class T>
+void Print(T& vec, int n){
+    cout << "Max Heap: [" << flush;
+    for (int i=0; i<n; i++){
+        cout << vec[i] << flush;
+        if (i < n-1){
+            cout << ", " << flush;
+        }
+    }
+    cout << "]" << endl;
+}
+ 
+ 
+int main() {
+ 
+    int a[] = {45, 35, 15, 30, 10, 12, 6, 5, 20, 50};
+    InsertA(a, 9);
+    Print(a, sizeof(a)/sizeof(a[0]));
+    cout << endl;
+ 
+    // STL based
+    vector<int> v = {45, 35, 15, 30, 10, 12, 6, 5, 20};
+    Print(v, v.size());
+    v.reserve(15);  // Reserve space for 15 elements
+ 
+    Insert(v, 50);
+    Print(v, v.size());
+ 
+    return 0;
+}

Heap/02 CreateHeapUsingSTLVector.cpp

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+#include <iostream>
+#include <vector>
+
+using namespace std;
+ 
+void Insert(vector<int>& vec, int key){
+    // Insert key at the end
+    auto i = vec.size();
+    vec.emplace_back(key);
+ 
+    // Rearrange elements: O(log n)
+    while (i > 0 && key > vec[i % 2 == 0 ? (i/2)-1 : i/2]){
+        vec[i] = vec[i % 2 == 0 ? (i/2)-1 : i/2];
+        i = i % 2 == 0 ? (i/2)-1 : i/2;
+    }
+    vec[i] = key;
+}
+ 
+void InsertInplace(int A[], int n){
+    int i = n;
+    int temp = A[n];
+    while (i > 0 && temp > A[i % 2 == 0 ? (i/2)-1 : i/2]){
+        A[i] = A[i % 2 == 0 ? (i/2)-1 : i/2];
+        i = i % 2 == 0 ? (i/2)-1 : i/2;
+    }
+    A[i] = temp;
+}
+ 
+void CreateHeap(vector<int>& vec, int A[], int n){
+    // O(n log n)
+    for (int i=0; i<n; i++){
+        Insert(vec, A[i]);
+    }
+}
+ 
+void createHeap(int A[], int n){
+    for (int i=0; i<n; i++){
+        InsertInplace(A, i);
+    }
+}
+ 
+template <class T>
+void Print(T& vec, int n, char c){
+    cout << c << ": [" << flush;
+    for (int i=0; i<n; i++){
+        cout << vec[i] << flush;
+        if (i < n-1){
+            cout << ", " << flush;
+        }
+    }
+    cout << "]" << endl;
+}
+ 
+ 
+int main() {
+ 
+    cout << "Create Heap" << endl;
+    int b[] = {10, 20, 30, 25, 5, 40, 35};
+    Print(b, sizeof(b)/sizeof(b[0]), 'b');
+ 
+    vector<int> v;
+    CreateHeap(v, b, sizeof(b)/sizeof(b[0]));
+    Print(v, v.size(), 'v');
+ 
+    cout << "Inplace Insert" << endl;
+    createHeap(b, sizeof(b)/sizeof(b[0]));
+    Print(b, sizeof(b)/sizeof(b[0]), 'b');
+ 
+ 
+    return 0;
+}