aaded binary-heap-implementation.c

data_structures/binary_trees/binary_heap_implimentation.c

@@ -0,0 +1,152 @@
+/* min_heap.c -- Min Binary Heap implementation in C */
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+
+typedef struct MinHeap {
+    int *arr;       // pointer to array of elements in heap
+    int capacity;   // maximum possible size
+    int size;       // current number of elements
+} MinHeap;
+
+/* create a new min heap with given initial capacity */
+MinHeap* createMinHeap(int capacity) {
+    MinHeap *h = (MinHeap*) malloc(sizeof(MinHeap));
+    if (!h) { perror("malloc"); exit(EXIT_FAILURE); }
+    h->capacity = capacity > 0 ? capacity : 10;
+    h->size = 0;
+    h->arr = (int*) malloc(sizeof(int) * h->capacity);
+    if (!h->arr) { perror("malloc"); exit(EXIT_FAILURE); }
+    return h;
+}
+
+/* free heap */
+void freeMinHeap(MinHeap *h) {
+    if (!h) return;
+    free(h->arr);
+    free(h);
+}
+
+/* helper: swap */
+static void swap(int *a, int *b) {
+    int tmp = *a;
+    *a = *b;
+    *b = tmp;
+}
+
+/* helper: ensure capacity (resize if full) */
+static void ensureCapacity(MinHeap *h) {
+    if (h->size < h->capacity) return;
+    int newCap = h->capacity * 2;
+    int *newArr = (int*) realloc(h->arr, sizeof(int) * newCap);
+    if (!newArr) { perror("realloc"); exit(EXIT_FAILURE); }
+    h->arr = newArr;
+    h->capacity = newCap;
+}
+
+/* heapify up (after insert) */
+static void heapifyUp(MinHeap *h, int idx) {
+    while (idx > 0) {
+        int parent = (idx - 1) / 2;
+        if (h->arr[parent] > h->arr[idx]) {
+            swap(&h->arr[parent], &h->arr[idx]);
+            idx = parent;
+        } else break;
+    }
+}
+
+/* heapify down (after extract/min removed) */
+static void heapifyDown(MinHeap *h, int idx) {
+    int left, right, smallest;
+    while (1) {
+        left = 2 * idx + 1;
+        right = 2 * idx + 2;
+        smallest = idx;
+
+        if (left < h->size && h->arr[left] < h->arr[smallest])
+            smallest = left;
+        if (right < h->size && h->arr[right] < h->arr[smallest])
+            smallest = right;
+        if (smallest != idx) {
+            swap(&h->arr[idx], &h->arr[smallest]);
+            idx = smallest;
+        } else break;
+    }
+}
+
+/* Insert a key into the heap (O(log n)) */
+void insertKey(MinHeap *h, int key) {
+    ensureCapacity(h);
+    h->arr[h->size] = key;
+    h->size += 1;
+    heapifyUp(h, h->size - 1);
+}
+
+/* Get minimum without removing (Peek) (O(1)) */
+int getMin(MinHeap *h) {
+    if (h->size == 0) return INT_MIN; // or handle error
+    return h->arr[0];
+}
+
+/* Extract min (remove and return minimum element) (O(log n)) */
+int extractMin(MinHeap *h) {
+    if (h->size <= 0) return INT_MIN; // indicate empty
+    int root = h->arr[0];
+    h->arr[0] = h->arr[h->size - 1];
+    h->size -= 1;
+    if (h->size > 0) heapifyDown(h, 0);
+    return root;
+}
+
+/* Search for a value (linear scan) O(n). Returns index or -1 if not found */
+int searchHeap(MinHeap *h, int value) {
+    for (int i = 0; i < h->size; ++i)
+        if (h->arr[i] == value) return i;
+    return -1;
+}
+
+/* Display the heap array (level-order) O(n) */
+void displayHeap(MinHeap *h) {
+    if (h->size == 0) {
+        printf("(empty heap)\n");
+        return;
+    }
+    printf("Heap (size=%d): ", h->size);
+    for (int i = 0; i < h->size; ++i) {
+        printf("%d ", h->arr[i]);
+    }
+    printf("\n");
+}
+
+/* Example usage */
+int main(void) {
+    MinHeap *heap = createMinHeap(10);
+
+    int values[] = { 20, 5, 15, 22, 40, 3, 8, 1, 30 };
+    int n = sizeof(values) / sizeof(values[0]);
+
+    printf("Inserting values: ");
+    for (int i = 0; i < n; ++i) {
+        printf("%d ", values[i]);
+        insertKey(heap, values[i]);
+    }
+    printf("\n");
+    displayHeap(heap);
+
+    printf("Min element (peek): %d\n", getMin(heap));
+
+    int s = 15;
+    int idx = searchHeap(heap, s);
+    if (idx >= 0) printf("Found %d at index %d (heap array index)\n", s, idx);
+    else printf("%d not found in heap\n", s);
+
+    printf("Extracting min elements:\n");
+    while (heap->size > 0) {
+        int m = extractMin(heap);
+        printf("%d ", m);
+    }
+    printf("\n");
+
+    freeMinHeap(heap);
+    return 0;
+}