C Exercises: Stack push, pop, get middle, and delete middle elements

C Stack: Exercise-13 with Solution

Write a C program to implement a stack that supports push, pop, get middle, and delete middle elements.

Sample Solution:

C Code:

#include <stdio.h>
#include <stdlib.h>

struct Node {
    int data;
    struct Node* next;
    struct Node* prev;
};

struct Stack {
    struct Node* top;
    struct Node* middle;
    int ctr;
};

void push(struct Stack* stack, int data) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = data;
    newNode->prev = NULL;
    newNode->next = stack->top;
    
    if (stack->ctr == 0) {
        stack->middle = newNode;
    } else if (stack->ctr % 2 == 0) {
        stack->middle = stack->middle->prev;
    }
    
    if (stack->top != NULL) {
        stack->top->prev = newNode;
    }
    
    stack->top = newNode;
    stack->ctr++;
}

int pop(struct Stack* stack) {
    if (stack->ctr == 0) {
        printf("Stack is underflow\n");
        return -1;
    }
    
    struct Node* top_node = stack->top;
    int data = top_node->data;
    
    stack->top = top_node->next;
    
    if (stack->top != NULL) {
        stack->top->prev = NULL;
    }
    
    free(top_node);
    
    if (stack->ctr % 2 == 1) {
        stack->middle = stack->middle->next;
    }
    
    stack->ctr--;
    
    return data;
}

int get_middle(struct Stack* stack) {
    if (stack->ctr == 0) {
        printf("Stack is empty\n");
        return -1;
    }
    
    return stack->middle->data;
}

void deleteMiddle(struct Stack* stack) {
    if (stack->ctr == 0) {
        printf("Stack is empty\n");
        return;
    }
    
    struct Node* middle_node = stack->middle;
    
    if (stack->ctr == 1) {
        stack->top = NULL;
        stack->middle = NULL;
    } else {
        stack->middle = stack->ctr % 2 == 0 ? stack->middle->next : stack->middle->prev;
        middle_node->prev->next = middle_node->next;
        middle_node->next->prev = middle_node->prev;
    }
    
    free(middle_node);
    stack->ctr--;
}

void printStack(struct Stack* stack) {
    if (stack->ctr == 0) {
        printf("Stack is empty\n");
        return;
    }
    
    struct Node* current = stack->top;
    while (current != NULL) {
        printf("%d ", current->data);
        current = current->next;
    }
    printf("\n");
}

int main() {
    struct Stack stack = {NULL, NULL, 0};    
    push(&stack, 23);
    push(&stack, 32);
    push(&stack, 26);
    push(&stack, 15);
    push(&stack, 88);    
    printf("Stack elements: ");
    printStack(&stack);     
    printf("Middle element: %d\n", get_middle(&stack)); 
    printf("\nDelete the middle element of the said stack:");
    deleteMiddle(&stack);
    printf("\nStack elements: ");
    printStack(&stack); 
    printf("Middle element: %d\n", get_middle(&stack)); 
    printf("\nDelete the middle element of the said stack:");
	deleteMiddle(&stack);    
    printf("\nStack elements: ");
    printStack(&stack);
    printf("Middle element: %d\n", get_middle(&stack));  
}

Sample Output:

Stack elements: 88 15 26 32 23 
Middle element: 26

Delete the middle element of the said stack:
Stack elements: 88 15 32 23 
Middle element: 15

Delete the middle element of the said stack:
Stack elements: 88 32 23 
Middle element: 32

Flowchart:

C Programming Code Editor:

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