Description: You have developed a maps application, which shows roads with traffic. You want to find out avergae speed on each road segment. You are given <start, end, speed> of cars. Find the average speed on each segment.
Example Input: [[0, 14, 90], [3, 15, 80]]
Output: [[0,3, 90], [3, 14, 85], [14, 15, 80]]