Page 74 - DCAP605_ADVANCED_DATA_STRUCTURE_AND_ALGORITHMS
P. 74
Unit 3: Stacks
} Notes
char stackTop(stk *stack) /* return the top value of the stack without popping
the stack */
{
if ( !(isEmpty(stack)) )
return stack->data[stack->top];
else
return ‘\0’;
}
int isEmpty(stk *stack) /* determine if stack is empty */
{
if ( stack->top == -1 ) /* empty */
return 1;
else /* not empty */
return 0;
}
int isFull(stk *stack) /* determine if stack is full */
{
if ( stack->top == 19 ) /* full */
return 1;
else /* not full */
return 0;
}
void printResult(char infix[], char postfix[]) /* display the result postfix
expression */
{
printf(“\n\n”); /*system(“cls”);*/
printf(“Infix notation : %s\n”, infix);
printf(“Postfix notation: %s\n\n”, postfix);
}
Here are some results of the test run.
Infi x Postfi x
(1+2)-(3*4/5)+6 12+34*5/-6+
1-2*3/(4-5) 123*45-/-
(1*2^3)-(4%3-5)^6 123^*43%5-6^-
Evaluating Postfi x Expression
An expression may be evaluated by making a left to right scan, stacking operands and evaluating
operators using the correct number of operands from the stack and finally placing back the result
on to the stack.
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