Infix to Postfix Conversion Using Stack in DSA C - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this infix to postfix conversion?

Given the infix expression A+B*C, what is the resulting postfix expression after conversion using a stack?

DSA C

Input: A+B*C
Output: ?

A AB+C*

B AB*C+

C A+BC*

D ABC*+

💡 Hint

Remember that multiplication (*) has higher precedence than addition (+).

In infix to postfix conversion, operators with higher precedence are placed before lower precedence operators in postfix. So B*C is evaluated first, then added to A.

❓ Predict Output

intermediate

What is the postfix expression for this infix with parentheses?

Convert the infix expression (A+B)*C to postfix using stack-based conversion. What is the output?

DSA C

Input: (A+B)*C
Output: ?

A AB+C*

B ABC+*

C A+BC*

D AB*+C

💡 Hint

Parentheses force the addition to happen before multiplication.

Parentheses mean A+B is evaluated first, so in postfix it becomes AB+, then multiplied by C, so AB+C*.

❓ Predict Output

advanced

What is the postfix output of this complex infix expression?

Convert the infix expression A+B*C-D/E to postfix using stack conversion. What is the correct postfix expression?

DSA C

Input: A+B*C-D/E
Output: ?

A AB+C*D/E-

B AB+C*DE/-

C ABC*+DE/-

D ABC*+D/E-

💡 Hint

Remember operator precedence: * and / before + and -, and left to right for same precedence.

First B*C and D/E are evaluated, then added and subtracted accordingly. So postfix is ABC*+DE/-.

🔧 Debug

advanced

Identify the error in this infix to postfix conversion snippet

This C code snippet attempts to convert infix to postfix but produces wrong output. What is the main logical error?

DSA C

char stack[100];
int top = -1;
void push(char c) { stack[++top] = c; }
char pop() { return stack[top--]; }

// Infix: A+B*C
// Code pushes operators without checking precedence properly.

// What is the error?

A Operands are pushed onto stack instead of output

B Operators are pushed without popping higher precedence operators first

C Stack overflow is not checked before push

D Pop function returns wrong element

💡 Hint

Check how operator precedence affects when to pop from stack.

The main error is not popping operators with higher or equal precedence before pushing a new operator, which breaks postfix order.

🧠 Conceptual

expert

What is the maximum stack size needed for converting an infix expression of length n?

Given an infix expression of length n (including operands, operators, and parentheses), what is the maximum number of elements that the operator stack can hold during infix to postfix conversion?

A n (all characters could be operators or parentheses)

B n/2 (half the expression length)

C n-1 (one less than expression length)

D Depends on the number of operators only

💡 Hint

Consider the worst case where all characters are operators or parentheses that stay on stack.

In the worst case, all characters except operands could be operators or parentheses pushed onto the stack, so maximum size is n.