f2e5e26af3
Correct: `Array.from()` (it’s a static method) Incorrect: `Array.join()` (doesn’t exist; it’s a prototype method) This patch uses the common `#` syntax to denote `.prototype.`.
1.9 KiB
solveRPN
Solves the given mathematical expression in reverse polish notation.
Throws appropriate errors if there are unrecognized symbols or the expression is wrong. The valid operators are :- +,-,*,/,^,** (^&** are the exponential symbols and are same). This snippet does not supports any unary operators.
Use a dictionary, OPERATORS to specify each operator's matching mathematical operation.
Use String.prototype.replace() with a regular expression to replace ^ with **, String.prototype.split() to tokenize the string and Array.prototype.filter() to remove empty tokens.
Use Array.prototype.forEach() to parse each symbol, evaluate it as a numeric value or operator and solve the mathematical expression.
Numeric values are converted to floating point numbers and pushed to a stack, while operators are evaluated using the OPERATORS dictionary and pop elements from the stack to apply operations.
const solveRPN = rpn => {
const OPERATORS = {
'*': (a, b) => a * b,
'+': (a, b) => a + b,
'-': (a, b) => a - b,
'/': (a, b) => a / b,
'**': (a, b) => a ** b
};
const [stack, solve] = [
[],
rpn
.replace(/\^/g, '**')
.split(/\s+/g)
.filter(el => !/\s+/.test(el) && el !== '')
];
solve.forEach(symbol => {
if (!isNaN(parseFloat(symbol)) && isFinite(symbol)) {
stack.push(symbol);
} else if (Object.keys(OPERATORS).includes(symbol)) {
const [a, b] = [stack.pop(), stack.pop()];
stack.push(OPERATORS[symbol](parseFloat(b), parseFloat(a)));
} else {
throw `${symbol} is not a recognized symbol`;
}
});
if (stack.length === 1) return stack.pop();
else throw `${rpn} is not a proper RPN. Please check it and try again`;
};
solveRPN('15 7 1 1 + - / 3 * 2 1 1 + + -'); // 5
solveRPN('2 3 ^'); // 8