Update employee-free-time.py

Author: kamyu104

Python/employee-free-time.py

@@ -1,6 +1,32 @@
 # Time:  O(m * logn), m is the number of schedule, n is the number of employees, m >= n
 # Space: O(n)
 
+# We are given a list schedule of employees, which represents the working time for each employee.
+# Each employee has a list of non-overlapping Intervals, and these intervals are in sorted order.
+# Return the list of finite intervals representing common, positive-length free time for all employees, also in sorted order.
+#
+# Example 1:
+# Input: schedule = [[[1,2],[5,6]],[[1,3]],[[4,10]]]
+# Output: [[3,4]]
+# Explanation:
+# There are a total of three employees, and all common
+# free time intervals would be [-inf, 1], [3, 4], [10, inf].
+# We discard any intervals that contain inf as they aren't finite.
+#
+# Example 2:
+# Input: schedule = [[[1,3],[6,7]],[[2,4]],[[2,5],[9,12]]]
+# Output: [[5,6],[7,9]]
+# (Even though we are representing Intervals in the form [x, y],
+#  the objects inside are Intervals, not lists or arrays.
+#  For example, schedule[0][0].start = 1, schedule[0][0].end = 2,
+# and schedule[0][0][0] is not defined.)
+#
+# Also, we wouldn't include intervals like [5, 5] in our answer, as they have zero length.
+#
+# Note:
+# - schedule and schedule[i] are lists with lengths in range [1, 50].
+# - 0 <= schedule[i].start < schedule[i].end <= 10^8.
+
 # Definition for an interval.
 # class Interval(object):
 #     def __init__(self, s=0, e=0):