23. Interval_List_Intersections.java

class Solution {
    public int[][] intervalIntersection(int[][] A, int[][] B) {
        List<int[]> ans = new ArrayList();
        int i = 0, j = 0;

        while (i < A.length && j < B.length) {
      // Let's check if A[i] intersects B[j].
            int lo = Math.max(A[i][0], B[j][0]);    // lo - the startpoint of the intersection
            int hi = Math.min(A[i][1], B[j][1]);    // hi - the endpoint of the intersection
            if (lo <= hi)
                ans.add(new int[]{lo, hi});

      // Remove the interval with the smallest endpoint
            if (A[i][1] < B[j][1])
                i++;
            else
                j++;
        }
        return ans.toArray(new int[ans.size()][]);
    }
}