feat(icake): add p4 solution and doctest

ISSUES: 1) Sort out previous brute force solution
2) Add unit tests or delete the unit test setup

Author: Jessica Yung

interview-cake/p4.py

@@ -0,0 +1,69 @@
+"""
+InterviewCake Problem 4
+
+Let's work with two tuples at a time, e.g. (3,5) and (4,8).
+There is overlap (i.e. they should merge if
+(1) tuple_one[0] <= tuple_two[0] and tuple_one[1] >= tuple_two[0]
+                  or the other way round (switch tuples 1,2)
+Can take a greedy approach -> merge as we go.
+
+...
+Insight: if you don't merge with any tuples the first run through, you will NEVER merge with any of the tuples.
+So we should compare the first tuple with every other tuple. And then we can throw it away.
+
+>>> condense_meeting_times_alt([(0, 1), (3, 5), (4, 8), (10, 12), (9, 10)])
+[(0, 1), (3, 8), (9, 12)]
+
+
+"""
+import unittest
+
+
+def condense_meeting_times_alt(meeting_times):
+    sorted_meeting_times = sorted(meeting_times)
+    merged_meetings = [meeting_times[0]]
+
+    for current_meeting_start, current_meeting_end in sorted_meeting_times[1:]:
+        last_merged_meeting_start, last_merged_meeting_end = merged_meetings[-1]
+        # If current and last_merged_meeting overlap:
+        if current_meeting_start <= last_merged_meeting_end:
+            merged_meetings[-1] = (last_merged_meeting_start, max(last_merged_meeting_end, current_meeting_end))
+
+        # Else add current meeting since it doesn't overlap
+        else:
+            merged_meetings.append((current_meeting_start, current_meeting_end))
+    return merged_meetings
+
+
+def merge(first, second):
+    return first[0], second[1]
+
+
+def condense_meeting_times(list_of_tuples):
+    """Rubbish."""
+    new_list_of_tuples = []
+    index = 0
+    list_len = len(list_of_tuples)
+    action_two_tuples(list_of_tuples[0], list_of_tuples[1], list_of_tuples)
+    while index + 1 < list_len:
+        for j in range(index + 1, list_len):
+            action_two_tuples(list_of_tuples[index], list_of_tuples[j], new_list_of_tuples)
+
+
+def action_two_tuples(first_index, second_index, tuples_list):
+    """Also rubbish."""
+    first = tuples_list[first_index]
+    second = tuples_list[second_index]
+    if first[0] <= second[0]:
+        if first[1] >= second[0]:
+            # TODO: list append merged times properly
+            tuples_list.append(merge(first_index, second_index))
+            # TODO: delete(first, second)
+    else:
+        # i.e. we know first[0] > second[0]
+        if second[1] >= first[0]:
+            # TODO: list append merged, delete prev
+            merge(second_index, first_index)
+
+if __name__ == '__main__':
+    unittest.main()