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DS/C/Lab/Week5/QueueStack.c

@@ -0,0 +1,84 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#define MAX_SIZE 100
+
+typedef struct {
+    int items[MAX_SIZE];
+    int top;
+} Stack;
+
+Stack* createStack() {
+    Stack* s = (Stack*)malloc(sizeof(Stack));
+    s->top = -1;
+    return s;
+}
+
+void push(Stack* s, int x) {
+    if (s->top == MAX_SIZE - 1) {
+        printf("Stack Overflow\n");
+        return;
+    }
+    s->items[++(s->top)] = x;
+}
+
+int pop(Stack* s) {
+    if (s->top == -1) {
+        printf("Stack Underflow\n");
+        return -1;
+    }
+    return s->items[(s->top)--];
+}
+
+int isEmpty(Stack* s) {
+    return s->top == -1;
+}
+
+typedef struct {
+    Stack* s1;
+    Stack* s2;
+} Queue;
+
+Queue* createQueue() {
+    Queue* q = (Queue*)malloc(sizeof(Queue));
+    q->s1 = createStack();
+    q->s2 = createStack();
+    return q;
+}
+
+void enqueue(Queue* q, int x) {
+    push(q->s1, x);
+}
+
+int dequeue(Queue* q) {
+    int x;
+    if (isEmpty(q->s1) && isEmpty(q->s2)) {
+        printf("Queue is empty\n");
+        return -1;
+    }
+    if (isEmpty(q->s2)) {
+        while (!isEmpty(q->s1)) {
+            x = pop(q->s1);
+            push(q->s2, x);
+        }
+    }
+    return pop(q->s2);
+}
+
+int main() {
+    Queue* q = createQueue();
+    
+    enqueue(q, 1);
+    enqueue(q, 2);
+    enqueue(q, 3);
+    
+    printf("%d\n", dequeue(q));
+    printf("%d\n", dequeue(q));
+    
+    enqueue(q, 4);
+    
+    printf("%d\n", dequeue(q));
+    printf("%d\n", dequeue(q));
+    
+    return 0;
+}