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Exercise 2 - Heap (Week 3)/Ex2.txt

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Exercise 2 - Heap (Week 3)/ex2.c

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+/* License: AGPLv3 or later. https://www.gnu.org/licenses/licenses.html
+ * 
+ * Exercise 2 - Implementing a heap (Week 3)
+ * Name: Manish
+ * Student Login: *****
+ * 
+ * Compile as:
+ * $ gcc -std=c11 -Wall -o ex2 ex2.c
+ */
+
+// assert used only for testing heap property
+// #include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int heap[100];
+int size = 0;
+
+void makeheap();
+void shiftdown(int index);
+// void shiftup(int index);
+// void swap(int i, int j);
+// int min(int i, int j);
+// void test_heap();
+// int is_bigger_or_equal(int bigger, int smaller);
+
+int main(void)
+{
+    printf("Enter file name: ");
+    char filename[257];
+    // Assuming filename/file path won't be longer than 256 characters
+    scanf("%256s", filename);
+
+    FILE* file = fopen(filename, "r");
+    if (!file)
+    {
+        perror(filename);
+        exit(EXIT_FAILURE);
+    }
+
+    // Trailing whitespace to consume all subsequent ' ', \t, \n, \r
+    while (fscanf(file, " %d ", &heap[size]) != EOF)
+    {
+        size++;
+    }
+
+    fclose(file);
+
+    makeheap();
+    
+    // test_heap();
+
+    // int upto = min(5, size);
+    // Assuming at least 5 integers will be read (else segfault!)
+    for (int i = 0; i < 5; i++)
+    {
+        printf("%d ", heap[i]);
+    }
+    printf("\n");
+
+    return 0;
+}
+
+void makeheap()
+{
+    // Shiftdown Method
+    int shiftdowns_required = (size / 2)-1;
+    for (int i = shiftdowns_required; i >= 0; i--)
+    {
+        shiftdown(i);
+    }
+
+    // Shiftup method
+    /*for (int i = 0; i < size; i++)
+    {
+       shiftup(i);
+    }*/
+}
+
+void shiftdown(int index)
+{
+    int child;
+    int temp; // used for swapping
+    // Loop instead of recursion for efficiency
+    while (1)
+    {
+        child = (index * 2) + 1;
+        // Reached end of tree
+        if (child >= size)
+        {
+            return;
+        }
+        // Has only one child
+        if (child + 1 >= size)
+        {
+        }
+        // Has both children
+        else
+        {
+            // Pick the bigger child
+            if (heap[child] < heap[child + 1])
+            {
+                child = child + 1;
+            }
+        }
+        if (heap[index] < heap[child])
+        {
+            // swap
+            temp = heap[index];
+            heap[index] = heap[child];
+            heap[child] = temp;
+            
+            index = child;
+        }
+        else
+        {
+            return;
+        }
+    }
+}
+/*
+void shiftup(int index)
+{
+    int parent;
+    int temp; // used for swapping
+    while (1)
+    {
+        if (index == 0)
+        {
+            return;
+        }
+        parent = (index - 1) / 2;
+        if (parent >= 0)
+        {
+            if (heap[parent] < heap[index])
+            {
+                // swap
+                temp = heap[index];
+                heap[index] = heap[parent];
+                heap[parent] = temp;
+            
+                index = parent;
+            }
+            else
+            {
+                return;
+            }
+        }
+        else
+        {
+            return;
+        }
+    }
+}*/
+/*
+inline void swap(int i, int j)
+{
+    int temp = heap[i];
+    heap[i] = heap[j];
+    heap[j] = temp;
+}*/
+/*
+inline int min(int i, int j)
+{
+    if (i < j)
+    {
+        return i;
+    }
+    return j;
+}*/
+/*
+void test_heap()
+{
+    int checks_required = (size/2)+1;
+    int child;
+    for (int i=0; i < checks_required; i++)
+    {
+        // Left child
+        child = (i*2)+1;
+        assert(is_bigger_or_equal(i, child));
+        // Right child
+        assert(is_bigger_or_equal(i, ++child));
+    }
+}
+
+inline int is_bigger_or_equal(int bigger, int smaller)
+{
+    if (bigger < size && smaller < size)
+    {
+        return (heap[bigger] >= heap[smaller]);
+    }
+    return 1;
+}
+*/

Exercise 2 - Heap (Week 3)/makefile

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+ex2:	ex2.c
+	gcc -Wall -std=c11 -o ex2 ex2.c