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update RPN solver

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This commit is contained in:
Rohit Tanwar
2018-01-01 22:00:12 +05:30
parent ff9a4ff546
commit 3742dff530
1 changed files with 11 additions and 22 deletions
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33
snippets/RPNSolver.md
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@ -1,32 +1,21 @@
### RPNSolver
Solves the given reverse polish notation
```js
``` js
const RPNSolver = RPN => {
const isNumeric = str => !isNaN(parseFloat(str)) && isFinite(str);
const isOperator = str => ['*','-','+','/','**'].includes(str)
let stack = [];
let solve = RPN.replace(/\^/g,'**').split(/\s+/g);
const operators = {'*' : (a,b) => a * b, '+' : (a,b) => a + b, '-' : (a,b) => a - b, '/' : (a,b) => a / b, '**': (a,b) => a ** b}
let [stack,solve] = [[],RPN.replace(/\^/g,'**').split(/\s+/g).filter(el => !/\s+/.test(el) && el !== '')]
solve.forEach(symbol => {
if(isNumeric(symbol)) {stack.push(symbol)}
else if (isOperator(symbol)){
a = stack.pop();
b = stack.pop();
if(symbol === "+") {
stack.push(parseFloat(a) + parseFloat(b));
} else if(symbol === "-") {
stack.push(parseFloat(b) - parseFloat(a));
} else if(symbol === "*") {
stack.push(parseFloat(a) * parseFloat(b));
} else if(symbol === "/") {
stack.push(parseFloat(b) / parseFloat(a));
} else if(symbol === "**") {
stack.push(parseFloat(a) ** parseFloat(b));
}
} else { console.log('Wrong RPN')}
if(!isNaN(parseFloat(symbol)) && isFinite(symbol)) {stack.push(symbol)}
else if (Object.keys(operators).includes(symbol)) {
let [a,b] = [stack.pop(),stack.pop()]
stack.push(operators[symbol](parseFloat(b),parseFloat(a)))
} else { throw `${symbol} is not a recognized symbol` }
}
)
return stack.length === 1 ? stack.pop : console.log("error")
if(stack.length === 1) return stack.pop()
else throw `${RPN} is not a proper RPN. Please check it and try again`
}
```