46d28f8b5e
Add the list of supported operators and specify that unary operators are not supported. Also tell that `^` & `**` are the same and are exponential operators(as `^` can be confused to be the xOR symbol)
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.replace() with a regular expression to replace ^ with **, String.split() to tokenize the string and Array.filter() to remove empty tokens.
Use Array.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('3 5 6 + *'); //33
solveRPN('2 4 / 5 6 - *'); //-0.5
solveRPN('2 3 ^'); //8
solveRPN('2 3 ^'); //8