Given two lists of disjoint, sorted intervals `firstList` and `secondList`, return the intersection of these two interval lists. **Pattern focus:** Merge Overlapping Ranges. Handle cases where intervals overlap at edges.
Example 1:
Input:
firstList = [[0,2],[5,10],[13,23],[24,25]] secondList = [[1,5],[8,12],[15,24],[25,26]]
Output:
[[1,2],[5,5],[8,10],[15,23],[24,24],[25,25]]
Explanation:
Intersecting intervals produce overlapping segments.
Example 2:
Input:
firstList = [[1,3],[6,7]] secondList = [[2,4],[7,8]]
Output:
[[2,3],[7,7]]
Explanation:
Intersection of [1,3]∩[2,4]=[2,3] and [6,7]∩[7,8]=[7,7].