Merge pull request #1276 from ivan1016017/may20

 adding summary ranges algo

Author: ivanpenaloza

src/my_project/interviews/top_150_questions_round_16/summary_ranges.py

@@ -0,0 +1,28 @@
+from typing import List, Union, Collection, Mapping, Optional
+from abc import ABC, abstractmethod
+
+class Solution:
+    def summaryRanges(self, nums: List[int]) -> List[str]:
+
+        len_nums = len(nums)
+
+        if len_nums == 0:
+            return []
+        elif len_nums == 1:
+            return [f'{nums[0]}']
+        else:
+            answer = list()
+
+            pre = start = nums[0]
+
+            for i in nums[1:]:
+                if i - pre > 1: 
+                    answer.append(f'{start}->{pre}' if pre-start > 0 else 
+                                  f'{start}')
+                    start = i 
+                pre = i 
+
+            answer.append(f'{start}->{pre}' if pre-start > 0 else f'{start}')
+
+            return answer
+

tests/test_150_questions_round_16/test_summary_ranges_round_16.py

@@ -0,0 +1,24 @@
+import unittest
+from src.my_project.interviews.top_150_questions_round_16\
+.summary_ranges import Solution
+
+class SummaryRangesTestCase(unittest.TestCase):
+
+    def test_empty(self):
+        solution = Solution()
+        output = solution.summaryRanges(nums=[])
+        target = []
+        self.assertEqual(target, output)
+
+    def test_single_element(self):
+        solution = Solution()
+        output = solution.summaryRanges(nums=[1])
+        target = ['1']
+        self.assertEqual(target, output)
+
+    def test_several_elements(self):
+        solution = Solution()
+        output = solution.summaryRanges(nums=[0,1,2,4,5,7])
+        target = ["0->2","4->5","7"]
+        for k, v in enumerate(target):
+            self.assertEqual(v, output[k])