Data Structure Slip No_9A

 #include <stdio.h>

#include <stdlib.h>

#include <ctype.h>

#define MAX_STACK_SIZE 100

 struct Stack

{    int top;

    int items[MAX_STACK_SIZE];

};

 void initializeStack(struct Stack* stack)

{    stack->top = -1;

}

void push(struct Stack* stack, int value)

{

    if (stack->top >= MAX_STACK_SIZE - 1)

   {

        printf("Stack Overflow\n");

        exit(1);

    }

    stack->items[++stack->top] = value;

}

 

int pop(struct Stack* stack)

{

    if (stack->top == -1)

   {

        printf("Stack Underflow\n");

        exit(1);

    }

  return stack->items[stack->top--];

}

 

int evaluatePostfix(char expression[], int values[])

{

    struct Stack stack;

    initializeStack(&stack);

 

    for (int i = 0; expression[i]; i++)

    {

        if (isdigit(expression[i]))

        {

            push(&stack, values[expression[i] - 'a']);

        }

else

{

            int operand2 = pop(&stack);

            int operand1 = pop(&stack);

            switch (expression[i])

   {

                case '+': push(&stack, operand1 + operand2); break;

                case '-': push(&stack, operand1 - operand2); break;

                case '*': push(&stack, operand1 * operand2); break;

                case '/': push(&stack, operand1 / operand2); break;

            }

        }

    }

    return pop(&stack);

}

 

void main()

{  char postfix[100];

    int values[26];

 

    printf("Enter postfix expression: ");

    scanf("%s", postfix);

 

    for (int i = 0; i < 26; i++) {

        printf("Enter value for %c: ", 'a' + i);

        scanf("%d", &values[i]);

    }

    printf("Answer: %d\n", evaluatePostfix(postfix, values));

}