Question

write an algorithm function called balance() in javascript that takes in a string and returns a strinf with balanced parantheses only. the string should be able to contain only parantheses, numbers, and letters. include comments of each portion of your code

balance(“()()”) should return “()()”

balance(“())”) should return “()”

balance(“a(b)c”) should return “a(b)c”

balance(“a(b)c())”) should return “a(b)c()”

Answer 1

function isValidString(s) {
var count = 0;
for (let c of s) { // check for equal number of brackets
if (c === '(') {
count++;
}
else if (c === ')') {
count--;
}
if (count < 0) return false;
}
return count === 0; // return true if no extra brackets
}

function balance(s) {
let levels = [s]; // create array
while (true) { // run till condition is true
let valid = levels.filter(isValidString) ; // return string according to given condition
if (valid.length > 0) { // check length must be greater than 0
return new Set(valid);
}

// check validity of all possible substrings with one character removed.
let nextlevels = [];
for (let s of levels) {
for (let i = 0; i < s.length; i++) {
nextlevels.push(s.substring(0, i) + s.substring(i + 1));
}
}
levels = nextlevels;
}
}
console.log(balance('()()'));
console.log(balance('())'));
console.log(balance('a(b)c'));
console.log(balance('a(b)c())'));