Finding Intersection of Arrays of Intervals in JavaScript

Problem

JavaScript function that takes in two arrays, arr1 and arr2 of intervals which are pairwise disjoint and in sorted order.

A closed interval [a, b] (with a <= b) denotes the set of real numbers x with a <= x <= b.

The intersection of two closed intervals is a set of real numbers that is either empty, or can be represented as a closed interval. For example, the intersection of [1, 3] and [2, 4] is [2, 3].) Our function is supposed to return the intersection of these two interval arrays.

For example, if the input to the function is −

const arr1 = [[0,2],[5,10],[13,23],[24,25]];
const arr2 = [[1,5],[8,12],[15,24],[25,26]];

Then the output should be −

const output = [[1,2],[5,5],[8,10],[15,23],[24,24],[25,25]];

Example

The code for this will be −

 Live Demo

const arr1 = [[0,2],[5,10],[13,23],[24,25]];
const arr2 = [[1,5],[8,12],[15,24],[25,26]];
const findIntersection = function (A, B) {
   const res = []
   let i = 0
   let j = 0
   while (i < A.length && j < B.length) {
      const [a, b] = A[i]
      const [c, d] = B[j]
      const lo = Math.max(a, c)
      const hi = Math.min(b, d)
      if (lo <= hi) {
         res.push([Math.max(a, c), Math.min(b, d)])
      }
      if (b < d) {
         i++
      } else {
         j++
      }
   }
   return res
};
console.log(findIntersection(arr1, arr2));

Output

And the output in the console will be −

[
   [ 1, 2 ],
   [ 5, 5 ],
   [ 8, 10 ],
   [ 15, 23 ],
   [ 24, 24 ],
   [ 25, 25 ] 
]