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Prefix calculator using stack in JavaScript
We are required to make a calculator with the RPN (reverse polish notation) input method using Stacks in JavaScript.
Consider the following input array −
const arr = [1, 5, '+', 6, 3, '-', '/', 7, '*'];
Process −
1 is an operand, push to Stack.
5 is an operand, push to Stack.
'+' is an operator, pop 1 and 5, calculate them and push result to Stack.
6 is an operand, push to Stack.
3 is an operand, push to Stack.
'−' is an operator, pop 6 and 3, subtract them and push result to Stack.
'/' is an operator, pop 6 and 3, divided them and push result to Stack.
7 is an operand, push to Stack.
'*' is an operator, pop 2 and 7, multiply them and push result to Stack.
And finally, the output should be −
const output = 14;
Example
The code for this will be −
const arr = [1, 5, '+', 6, 3, '−', '/', 7, '*'];
const stackCalculator = (arr = []) => {
const options = {
'+': (a, b) => a + b,
'−': (a, b) => a - b,
'*': (a, b) => a * b,
'/': (a, b) => a / b
};
const stack = [];
arr.forEach(value => {
stack.push(value in options
? options[value](...stack.splice(-2))
: value
);
});
return stack;
};
console.log(stackCalculator(arr));Output
And the output in the console will be −
[14]
Updated on: 23-Nov-2020
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