thanhnguyennguyen / cff

const Stack = require('../index.js');

const operators = {

    "+": 1,

    "-": 1,

    "*": 2,

    "/": 2,

    "(": 3,

    ")": 4,

}

const infixToPostFix = (formula) => {

    let result = ""

    let stack = new Stack()

    for (let i = 0; i < formula.length; i++) {

        let c = formula[i]

        if (!operators[c]) {

            result += c

            continue

        }

        if (c == '(') {

            stack.push(c)

            continue

        }

        if (c == ')') {

            while (stack.top() != '(') {

                c = stack.pop()

                result += c

            }

            stack.pop() // pop '('

            continue

        }

        let top = stack.top()

        if (stack.isEmpty() || top == '(' || operators[c] > operators[top]) {

            stack.push(c)

        } else {

            while (!stack.isEmpty() && operators[top] >= operators[c]) {

                result += stack.pop()

            }

            stack.push(c)

        }

    }

    while (!stack.isEmpty()) {

        result += stack.pop()

    }

    return result

}

module.exports = infixToPostFix