Implementing Multiple Stacks in a Single Array: A Complete Guide for Beginners

In this article, we will explore the concept of multi-stack implementation in a single array, why it is important, and how you can implement it programmatically. Additionally, we’ll provide a clear example of implementing multiple stacks in C and conclude with insights into its applications.

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What is Multi-Stack Implementation?

Multi-stack implementation refers to the technique of managing more than one stack in a single array. It is especially useful in memory-constrained scenarios where dynamic memory allocation may not be feasible or efficient.

Why Use Multiple Stacks in One Array?

When only a single array is used to represent one stack, you are limited by the maximum size of that array. However, by implementing multiple stacks within the same array, you can:

Efficiently utilize memory.
Avoid the overhead of managing multiple arrays.
Enable two or more stacks to coexist without exceeding the combined array size.

For instance, if an array STACK[n] is used to represent two stacks, Stack A and Stack B:

Stack A grows from left to right.
Stack B grows from right to left.
The total size of Stack A and Stack B combined will never exceed n.

Program to Implement Multiple Stacks Using a Single Array

Below is a C program demonstrating how to implement two stacks in a single array:

#include<stdio.h>
#define MAX 10

int stack[MAX], topA = -1, topB = MAX;

// Push operation for Stack A
void pushA(int val) {
    if (topA + 1 == topB) {
        printf("\nOverflow in StackA");
        return;
    }
    stack[++topA] = val;
}

// Pop operation for Stack A
int popA() {
    if (topA == -1) {
        printf("\nUnderflow in StackA");
        return -999;
    }
    return stack[topA--];
}

// Display Stack A
void showA() {
    if (topA == -1) {
        printf("\nStackA is empty");
        return;
    }
    for (int i = topA; i >= 0; i--)
        printf("   %d", stack[i]);
}

// Push operation for Stack B
void pushB(int val) {
    if (topB - 1 == topA) {
        printf("\nOverflow in StackB");
        return;
    }
    stack[--topB] = val;
}

// Pop operation for Stack B
int popB() {
    if (topB == MAX) {
        printf("\nUnderflow in StackB");
        return -999;
    }
    return stack[topB++];
}

// Display Stack B
void showB() {
    if (topB == MAX) {
        printf("\nStackB is empty");
        return;
    }
    for (int i = topB; i < MAX; i++)
        printf("   %d", stack[i]);
}

void main() {
    int no, ch;
    do {
        printf("\n 1 PushA\n 2 PopA\n 3 ShowA\n 4 PushB\n 5 PopB\n 6 ShowB\n 0 Exit\n Enter your choice: ");
        scanf("%d", &ch);
        switch (ch) {
            case 1:
                printf("\nEnter number: ");
                scanf("%d", &no);
                pushA(no);
                break;
            case 2:
                no = popA();
                if (no != -999)
                    printf("\n%d popped", no);
                break;
            case 3:
                showA();
                break;
            case 4:
                printf("\nEnter number: ");
                scanf("%d", &no);
                pushB(no);
                break;
            case 5:
                no = popB();
                if (no != -999)
                    printf("\n%d popped", no);
                break;
            case 6:
                showB();
                break;
            case 0:
                break;
            default:
                printf("\nInvalid choice");
        }
    } while (ch != 0);
}

Key Insights from the Program

Efficient Memory Management: By sharing a single array between two stacks, memory usage is optimized.
Growth in Opposite Directions: Stack A grows from left to right, while Stack B grows from right to left, ensuring no memory overlap.
Overflow Prevention: The program prevents overflow by checking whether Stack A and Stack B are about to collide.

Advantages of Multi-Stack Implementation

Flexibility: You can adjust stack boundaries dynamically within the same array.
Improved Resource Utilization: Efficiently uses available memory.
Versatility: Ideal for scenarios where fixed array sizes may lead to memory wastage.

Conclusion

In this article, we introduced the concept of multi-stack implementation using a single array and provided a detailed C program to illustrate the process. We also highlighted how tools like Apache Hive can complement such programming techniques in managing and processing large datasets.

By mastering multiple stack implementation and tools like Hive, you can solve real-world programming challenges and excel in big data analytics.