2375.js

/** ------------------------------------------------------------------------------
 * 
 * 2375. Construct Smallest Number From DI String
 * Topics: Stack
 * https://leetcode.com/problems/construct-smallest-number-from-di-string/description/?envType=daily-question&envId=2025-02-18
 * 
 ------------------------------------------------------------------------------ */
/**
 * @param {string} pattern
 * @return {string}
 */
var smallestNumber = function (pattern) {
  const stack = []
  let result = ""

  for (let i = 0; i <= pattern.length; i++) {
    stack.push(i + 1)

    if (i === pattern.length || pattern[i] === "I") {
      while (stack.length) {
        result += stack.pop()
      }
    }
  }

  return result
}

/**
 * @param {string} pattern
 * @return {string}
 */
var smallestNumber = function (pattern) {
  let arr = Array.from({ length: pattern.length + 1 }).fill("")
  let nextNum = 1

  function fillBackward(idx) {
    for (let i = idx - 1; i >= 0; i--) {
      if (arr[i]) break

      arr[i] = nextNum++
    }
  }

  for (let i = 0; i < pattern.length; i++) {
    if (pattern[i] === "I") {
      arr[i] = nextNum++
      fillBackward(i)
    }
  }

  fillBackward(arr.length)
  return arr.join("")
}

console.log(smallestNumber("IIIDIDDD"))