{"id":534,"date":"2024-10-19T13:52:42","date_gmt":"2024-10-19T08:22:42","guid":{"rendered":"https:\/\/codexplained.in\/?p=534"},"modified":"2025-11-24T15:33:19","modified_gmt":"2025-11-24T10:03:19","slug":"implement-stack-using-linked-list","status":"publish","type":"post","link":"https:\/\/codexplained.in\/?p=534","title":{"rendered":"Implement Stack using Linked List"},"content":{"rendered":"
\n#include <stdio.h>\n#include <stdlib.h>\n\n\/\/ Define a structure for a linked list node\nstruct Node {\n    int data;\n    struct Node* next;\n};\n\n\/\/ Function to push an element onto the stack\nvoid push(struct Node** top, int value) {\n    \/\/ Create a new node\n    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));\n    if (!newNode) {\n        printf("Heap overflow\\n");\n        return;\n    }\n    \n    newNode->data = value;  \/\/ Set the data\n    newNode->next = *top;   \/\/ Link the new node to the current top\n    *top = newNode;         \/\/ Update the top to the new node\n    printf("Pushed %d onto the stack.\\n", value);\n}\n\n\/\/ Function to check if the stack is empty\nint isEmpty(struct Node* top) {\n    return top == NULL;\n}\n\n\/\/ Function to pop an element from the stack\nint pop(struct Node** top) {\n    if (isEmpty(*top)) {\n        printf("Stack underflow\\n");\n        return -1;\n    }\n    \n    struct Node* temp = *top; \/\/ Temporarily hold the top node\n    *top = (*top)->next;      \/\/ Update the top to the next node\n    int poppedValue = temp->data; \/\/ Retrieve the popped value\n    free(temp);               \/\/ Free the memory of the old top node\n    printf("Popped %d from the stack.\\n", poppedValue);\n    return poppedValue;\n}\n\n\/\/ Function to peek the top element of the stack\nint peek(struct Node* top) {\n    if (!isEmpty(top)) {\n        return top->data;\n    } else {\n        printf("Stack is empty\\n");\n        return -1;\n    }\n}\n\n\/\/ Function to display all elements in the stack\nvoid display(struct Node* top) {\n    if (isEmpty(top)) {\n        printf("Stack is empty\\n");\n    } else {\n        printf("Stack elements: ");\n        struct Node* temp = top;\n        while (temp != NULL) {\n            printf("%d ", temp->data);\n            temp = temp->next;\n        }\n        printf("\\n");\n    }\n}\n\nint main() {\n    struct Node* stack = NULL; \/\/ Initialize an empty stack\n\n    \/\/ Push elements onto the stack\n    push(&stack, 10);\n    push(&stack, 20);\n    push(&stack, 30);\n\n    \/\/ Display stack elements\n    display(stack);\n\n    \/\/ Peek at the top element\n    printf("Top element is %d\\n", peek(stack));\n\n    \/\/ Pop elements from the stack\n    pop(&stack);\n    pop(&stack);\n\n    \/\/ Display stack elements again\n    display(stack);\n\n    \/\/ Pop the last element\n    pop(&stack);\n\n    \/\/ Try to pop from an empty stack\n    pop(&stack);\n\n    return 0;\n}\n\n<\/pre><\/div>\n\n\n
Explanation:<\/h3>\n\n\n\n
    \n
  1. Structure Definition (struct Node<\/code>)<\/strong>:\n
      \n
    • The Node<\/code> structure represents each element in the stack.<\/li>\n\n\n\n
    • Each node stores an integer (data<\/code>) and a pointer to the next node (next<\/code>).<\/li>\n<\/ul>\n<\/li>\n\n\n\n
    • Push Function (push<\/code>)<\/strong>:\n
        \n
      • This function inserts a new element at the top of the stack.<\/li>\n\n\n\n
      • It creates a new node, sets its data<\/code> with the given value, and points it to the current top<\/code> node.<\/li>\n\n\n\n
      • Then, it updates the top<\/code> pointer to the new node, making it the new top of the stack.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
      • <\/li>\n\n\n\n
      • <\/li>\n\n\n\n
      • Pop Function (pop<\/code>)<\/strong>:\n
          \n
        • This function removes the element from the top of the stack.<\/li>\n\n\n\n
        • It first checks if the stack is empty to avoid underflow.<\/li>\n\n\n\n
        • If not empty, it updates the top<\/code> to point to the next node and frees the old top node’s memory.<\/li>\n\n\n\n
        • It returns the value of the popped node.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
        • Peek Function (peek<\/code>)<\/strong>:\n
            \n
          • This function returns the value of the top element without removing it.<\/li>\n\n\n\n
          • It checks if the stack is empty before attempting to access the top<\/code>‘s data.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
          • Display Function (display<\/code>)<\/strong>:\n
              \n
            • This function prints all the elements in the stack from top to bottom.<\/li>\n\n\n\n
            • It traverses from the top node to the bottom, printing each data<\/code>.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
            • Main Function (main<\/code>)<\/strong>:\n
                \n
              • The stack is initialized as NULL<\/code>, representing an empty stack.<\/li>\n\n\n\n
              • A few values are pushed onto the stack, displayed, and some are popped off to show how the stack shrinks.<\/li>\n\n\n\n
              • The program also attempts to pop from an empty stack to demonstrate the underflow handling.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n
                Pushed 10 onto the stack.\nPushed 20 onto the stack.\nPushed 30 onto the stack.\nStack elements: 30 20 10 \nTop element is 30\nPopped 30 from the stack.\nPopped 20 from the stack.\nStack elements: 10 \nPopped 10 from the stack.\nStack is empty\nStack underflow\n<\/code><\/pre>\n\n\n\n
                Explanation of the Output:<\/h3>\n\n\n\n
                  \n
                • Three elements (10, 20, and 30) are pushed onto the stack.<\/li>\n\n\n\n
                • When displayed, the stack shows elements as 30 20 10<\/code>, where 30<\/code> is at the top.<\/li>\n\n\n\n
                • After popping, the top element 30<\/code> is removed, followed by 20<\/code>.<\/li>\n\n\n\n
                • The display then shows 10<\/code> as the only element.<\/li>\n\n\n\n
                • Popping again removes 10<\/code>, leaving the stack empty.<\/li>\n\n\n\n
                • Attempting another pop results in a “Stack underflow” message since the stack is empty.<\/li>\n<\/ul>\n\n\n\n
                  This program effectively demonstrates the basic operations of a stack using a linked list, providing flexibility in terms of dynamic memory usage and avoiding the fixed size limitation of arrays.<\/p>\n