921.js

/** ------------------------------------------------------------------------------
 * 
 * 921. Minimum Add to Make Parentheses Valid
 * Topics: Stack, Greedy
 * https://leetcode.com/problems/minimum-add-to-make-parentheses-valid/?envType=daily-question&envId=2024-10-09
 * 
 ------------------------------------------------------------------------------ */
/**
 * @param {string} s
 * @return {number}
 */
var minAddToMakeValid = function (s) {
  const stack = []

  for (let c of s) {
    if (c === "(") {
      stack.push(c)
    } else {
      if (stack[stack.length - 1] === "(") {
        stack.pop()
      } else {
        stack.push(c)
      }
    }
  }
  return stack.length
}

/**
 * 천재
 */
var minAddToMakeValid = function (s) {
  let left = 0,
    right = 0

  for (let c of s) {
    if (c === "(") left++
    else if (!left) right++
    else left--
  }

  return left + right
}

console.log(minAddToMakeValid("())"))