exp 3,5,6,7: init

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

5.c

@@ -0,0 +1,72 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct Stacks stacks;
+struct Stacks {
+  int *stack;
+  uint s1, s2;
+  uint l1, l2;
+};
+
+stacks *init(uint s1, uint s2) {
+  stacks *s = malloc(sizeof(stacks));
+  s->stack = malloc(sizeof(int) * (s1 + s2));
+  s->s1 = s1, s->s2 = s2;
+  s->l1 = s->l2 = 0;
+
+  return s;
+}
+
+void push(uint stack, stacks *s, int elem) {
+  if (stack != 1 && stack != 2)
+    fprintf(stderr, "Invalid stack number\n");
+
+  if (stack == 1) {
+    if (s->l1 == s->s1) {
+      fprintf(stderr, "Stack 1 Overflow");
+      return;
+    }
+    s->stack[s->l1++] = elem;
+    return;
+  }
+
+  if (s->l2 == s->s2) {
+    fprintf(stderr, "Stack 2 Overflow");
+    return;
+  }
+  s->stack[s->s1 + s->l2++] = elem;
+}
+
+int pop(uint stack, stacks *s) {
+  if (stack != 1 && stack != 2)
+    fprintf(stderr, "Invalid stack number\n");
+
+  if (stack == 1) {
+    if (!s->l1) {
+      fprintf(stderr, "Stack 1 Underflow");
+      exit(1);
+    }
+    return s->stack[--s->l1];
+  }
+
+  if (!s->l2) {
+    fprintf(stderr, "Stack 2 Underflow");
+    exit(1);
+  }
+  return s->stack[s->s1 + --s->l2];
+}
+
+int main() {
+  int s1 = 8, s2 = 4; // sizes
+  stacks *s = init(s1, s2);
+  push(1, s, 3);
+  push(1, s, 99);
+  push(2, s, 6);
+  push(1, s, 4);
+
+  printf("%d ", pop(1, s));
+  printf("%d", pop(2, s));
+
+  free(s->stack);
+  free(s);
+}