Interval List Intersections

LeetCode Q 986 - Interval List Intersections

Given two lists of closed intervals, each list of intervals is pairwise disjoint and in sorted order.
Return the intersection of these two interval lists.
(Formally, a closed interval [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].)

Example 1: Input: A = [[0,2],[5,10],[13,23],[24,25]], B = [[1,5],[8,12],[15,24],[25,26]] ; Output: [[1,2],[5,5],[8,10],[15,23],[24,24],[25,25]]
Reminder: The inputs and the desired output are lists of Interval objects, and not arrays or lists.

Note:

• 0 <= A.length < 1000
• 0 <= B.length < 1000
• 0 <= A[i].start, A[i].end, B[i].start, B[i].end < 10^9

NOTE: input types have been changed on April 15, 2019. Please reset to default code definition to get new method signature.

Solution

Code:

public int[][] intervalIntersection(int[][] A, int[][] B) {
  int lenA = A.length, lenB = B.length;

  List<int[]> intervals = new ArrayList<>();

  for (int i = 0, j = 0; i < lenA && j < lenB; ) {
    int al = A[i][0], ar = A[i][1];
    int bl = B[j][0], br = B[j][1];

    int l = Math.max(al, bl), r = Math.min(ar, br);
    if (l <= r) intervals.add(new int[]{l, r});

    if (ar > br) j++;
    else if (ar < br) i++;
    else { i++; j++; }
  }

  int[][] res = new int[intervals.size()][2];
  res = intervals.toArray(res);
  //int index = 0;
  //for (int[] interval: intervals)
  //    res[index++] = interval;

  return res;
}