Stack • Applications

Infix to Postfix Conversion

Convert human-readable mathematical expressions into computer-friendly Postfix notation using a Stack to enforce operator precedence.

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Operands First

Letters and numbers (operands) never go into the stack. The moment you see them, they are appended directly to the output string.

The Stack of Operators

The stack ONLY holds operators and parentheses. It enforces precedence: a lower-precedence operator cannot be placed on top of a higher-precedence one.

The Parentheses Rule

An open parenthesis `(` is pushed unconditionally. A close parenthesis `)` forces the stack to pop all operators into the output until its matching `(` is found.

a+b*c

Operator Stack

Postfix Output

Code Tracker

:::

1function infixToPostfix(exp) {

2 let stack = []; let res = '';

3 for (let char of exp) {

4 if (isOperand(char)) res += char;

5 else if (char === '(') stack.push(char);

6 else if (char === ')') {

7 while (stack[stack.length-1] !== '(') res += stack.pop();

8 stack.pop();

9 } else {

10 while (stack.length && prec(char) <= prec(stack[stack.length-1])) {

11 res += stack.pop();

12 }

13 stack.push(char);

14 }

15 }

16 while(stack.length) res += stack.pop();

17 return res;

18}

Infix To Postfix

Infix To Postfix

Infix to Postfix Conversion

Operands First

The Stack of Operators

The Parentheses Rule

Infix to Postfix Conversion

Operands First

The Stack of Operators

The Parentheses Rule