exp 3,5,6,7: init

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

6.c

@@ -0,0 +1,48 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct Node node;
+struct Node {
+  int id;
+  struct Node *next;
+};
+
+int peek(node *stack) { return stack->id; }
+
+void push(node **stack, int id) {
+  node *new = malloc(sizeof(node));
+  new->id = id;
+
+  new->next = *stack;
+  *stack = new;
+}
+
+int pop(node **stack) {
+  int id = (*stack)->id;
+  node *next = (*stack)->next;
+  free(*stack);
+  *stack = next;
+  return id;
+}
+
+void traverse(node *stack) {
+  while (stack != NULL) {
+    printf("%d ", stack->id);
+    stack = stack->next;
+  }
+  printf("\n");
+}
+
+int main() {
+  node *stack = NULL;
+  push(&stack, 4);
+  push(&stack, 99);
+  push(&stack, 23);
+  printf("Pop: %d\n", pop(&stack));
+  printf("Traverseal: ");
+  traverse(stack);
+
+  // free
+  while (stack != NULL)
+    pop(&stack);
+}