Merge pull request #1844 from shriyadindi/patch-3

 Two Stacks to Implement a Queue

StackQueues/TwoStackstoImplementQueue/StackQueue.c

@@ -0,0 +1,98 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#define MAX 100
+
+// Stack structure with top pointer and array for elements
+typedef struct Stack {
+    int arr[MAX];
+    int top;
+} Stack;
+
+// Function to initialize a stack
+void initStack(Stack *stack) {
+    stack->top = -1;
+}
+
+// Function to check if a stack is empty
+int isEmpty(Stack *stack) {
+    return stack->top == -1;
+}
+
+// Function to check if a stack is full
+int isFull(Stack *stack) {
+    return stack->top == MAX - 1;
+}
+
+// Function to push an element onto a stack
+void push(Stack *stack, int data) {
+    if (isFull(stack)) {
+        printf("Stack overflow\n");
+        return;
+    }
+    stack->arr[++stack->top] = data;
+}
+
+// Function to pop an element from a stack
+int pop(Stack *stack) {
+    if (isEmpty(stack)) {
+        printf("Stack underflow\n");
+        return -1;
+    }
+    return stack->arr[stack->top--];
+}
+
+// Queue structure using two stacks
+typedef struct QueueUsingStacks {
+    Stack stack1;
+    Stack stack2;
+} QueueUsingStacks;
+
+// Function to initialize the queue
+void initQueue(QueueUsingStacks *queue) {
+    initStack(&queue->stack1);
+    initStack(&queue->stack2);
+}
+
+// Enqueue operation
+void enqueue(QueueUsingStacks *queue, int data) {
+    push(&queue->stack1, data);
+    printf("Enqueued %d\n", data);
+}
+
+// Dequeue operation
+int dequeue(QueueUsingStacks *queue) {
+    // If both stacks are empty, queue is empty
+    if (isEmpty(&queue->stack1) && isEmpty(&queue->stack2)) {
+        printf("Queue is empty\n");
+        return -1;
+    }
+
+    // Move elements from stack1 to stack2 if stack2 is empty
+    if (isEmpty(&queue->stack2)) {
+        while (!isEmpty(&queue->stack1)) {
+            push(&queue->stack2, pop(&queue->stack1));
+        }
+    }
+
+    // Pop from stack2, which is the front of the queue
+    int dequeuedValue = pop(&queue->stack2);
+    printf("Dequeued %d\n", dequeuedValue);
+    return dequeuedValue;
+}
+
+int main() {
+    QueueUsingStacks queue;
+    initQueue(&queue);
+
+    enqueue(&queue, 1);
+    enqueue(&queue, 2);
+    enqueue(&queue, 3);
+
+    dequeue(&queue);
+    dequeue(&queue);
+    dequeue(&queue);
+    dequeue(&queue);  // Queue is empty at this point
+
+    return 0;
+}