Binary Tree - inverse (mirror)

inverseBinaryTree.js

// Example 1:
// Input: root = [4,2,7,1,3,6,9]
// Output: [4,7,2,9,6,3,1]

// Example 2:
// Input: root = [4,2,7,1,3,6]
// Output: [4,7,2,6,3,1]

// Example 3:
// Input: root = [2,1,3]
// Output: [2,3,1]


function reverse(arr, startIndex, endIndex) {
  for (let i = startIndex; i <= Math.floor((startIndex + endIndex) / 2); i++) {
    let temp = arr[i];
    arr[i] = arr[endIndex - i + startIndex];
    arr[endIndex - i + startIndex] = temp;
  }  
}

function inverseBinaryTree(arr) {
  let i = 0;
  let toThePower = 0;

  while (i < arr.length) {
    const jump = Math.pow(2, toThePower);
    reverse(arr, i, Math.min(i + jump - 1, arr.length - 1));

    i = i + jump;
    toThePower += 1;
  }

  return arr;
}

inverseBinaryTree([4, 2, 7, 1, 3, 6, 9]);

inverseBinaryTree([4, 2, 7, 1, 3, 6]);

inverseBinaryTree([4, 2, 7, 1, 3]);