LeetCode: Replace Elements with Greatest Element on Right Side Solution

Approach

I prefer reverse array and iterate forward

Implementation (in-place operation)

1/**
2 * @param {number[]} arr
3 * @return {number[]}
4 */
5var replaceElements = function (arr) {
6  arr.reverse()
7
8  let max = -1
9
10  for (let i = 0; i < arr.length; i++) {
11    let temp = arr[i]
12    arr[i] = max
13    max = Math.max(max, temp)
14  }
15
16  return arr.reverse()
17}

Implementation (create new array)

1/**
2 * @param {number[]} arr
3 * @return {number[]}
4 */
5var replaceElements = function (arr) {
6  const reversedArr = [...arr].reverse()
7
8  let max = -1
9
10  const rightMax = reversedArr.map((_, index) => {
11    if (index === 0) return -1
12
13    max = Math.max(max, reversedArr[index - 1])
14    return max
15  })
16
17  return rightMax.reverse()
18}