Identical Subarrays

Create a function that takes in a two-dimensional array and returns the number of sub-arrays with only identical elements.

Examples

countIdentical([
  [1],
  [2],
  [3],
  [4]
]) ➞ 4

// Single-item arrays still count as having identical elements.

countIdentical([
  [1, 2],
  [2, 3],
  [3, 4],
  [4, 4]
]) ➞ 1

countIdentical([
  [33, 33],
  [5],
  ["a", "a"],
  [2, 2, 2],
  [1, 2, 2],
  [3, 1]
]) ➞ 4

// 4 arrays with identical elements: [33, 33], [5], ["a", "a"], and [2, 2, 2]

countIdentical([
  ["@", "@", "@", "@"],
  [2, 3], [3, 4], [4, 4]
]) ➞ 2

Notes

Single-element arrays count as (trivially) having identical elements.