Merge Sort (Tree Visualization)

function mergeSort(arr, left, right) {
  if (left >= right) return; // Base case (Leaf)
  let mid = Math.floor((left + right) / 2);
  
  // DIVIDE AND CONQUER
  mergeSort(arr, left, mid);      // Left
  mergeSort(arr, mid + 1, right); // Right
  
  // MERGE (Conquer)
  merge(arr, left, mid, right);
}

function merge(arr, left, mid, right) {
  let temp = [], i = left, j = mid + 1;
  while (i <= mid && j <= right) {
    if (arr[i] <= arr[j]) temp.push(arr[i++]);
    else temp.push(arr[j++]);
  }
  // Copy remaining elements...
  for (let k = 0; k < temp.length; k++) {
    arr[left + k] = temp[k]; // Write to parent array
  }
}