C Exercises: Find the maximum element in a stack

Last update on February 24 2025 07:02:32 (UTC/GMT +8 hours)

Write a C program to find the maximum element in a stack.

Sample Solution:

C Code:

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

#define MAX_SIZE 100

// Arrays to maintain the main stack and the stack for tracking maximum elements
int mainStack[MAX_SIZE];
int maxStack[MAX_SIZE];
int top = -1;     // Top index of the main stack
int max_top = -1; // Top index of the maximum stack

// Function to push an element onto the main stack
void push(int ele) {
    if (top >= MAX_SIZE - 1) {
        printf("Stack is full\n");
        return;
    }

    // Push the element onto the main stack
    top++;
    mainStack[top] = ele;

    // If the maxStack is empty or the element is greater than or equal to the top element in maxStack,
    // push the element onto the maxStack to track maximum elements
    if (max_top == -1 || ele >= maxStack[max_top]) {
        max_top++;
        maxStack[max_top] = ele;
    }
}

// Function to pop an element from the main stack
int pop() {
    if (top < 0) {
        printf("Stack is empty\n");
        return INT_MIN;
    }

    // Pop the top element from the main stack
    int ele = mainStack[top];
    top--;

    // If the popped element is the top element in maxStack, also pop it from maxStack
    if (ele == maxStack[max_top]) {
        max_top--;
    }

    return ele;
}

// Function to get the maximum element from the main stack
int getMax() {
    if (max_top < 0) {
        printf("Stack is empty\n");
        return INT_MIN;
    }

    return maxStack[max_top];
}

// Function to print the elements of the stack
void printstack(int *stack) {
    printf("Current stack elements:\n");
    for (int i = 0; i <= top; i++) {
        printf("%d ", stack[i]);
    }
}

int main() {
    // Example usage of the stack functions
    push(5);
    push(2);
    push(1);
    push(6);
    push(8);
    printstack(mainStack);
    printf("\nMaximum element: %d\n", getMax()); 
    pop();
    pop();
    printf("\nAfter removing two elements:\n");
    printstack(mainStack);
    printf("\nMaximum element: %d\n", getMax());  
    push(10);
    printf("\nAfter adding one element:\n");
    printstack(mainStack);
    printf("\nMaximum element: %d\n", getMax());      
    return 0;
}

Output:

Current stack elements:
5 2 1 6 8 
Maximum element: 8

After removing two elements:
Current stack elements:
5 2 1 
Maximum element: 5

After adding one element:
Current stack elements:
5 2 1 10 
Maximum element: 10

Flowchart:

Flowchart: Find the maximum element in a stack.

C Programming Code Editor:

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