add problem 77

Author: supercoderhawk

Python/sln_1_100/solution_71_80.py

@@ -1,4 +1,9 @@
 # -*- coding: utf-8 -*-
+from typing import List
+import copy
+import math
+
+
 class Solution_71_80(object):
     def simplifyPath(self, path):
         """
@@ -31,3 +36,27 @@ def simplifyPath(self, path):
                 final_path_segments.append(segment)
 
         return '/' + '/'.join(final_path_segments)
+
+    def combine(self, n: int, k: int) -> List[List[int]]:
+        """
+        77
+        :param n:
+        :param k:
+        :return:
+        """
+
+        results = []
+
+        def backtrace(res=[]):
+            if len(res) == k:
+                results.append(res)
+            else:
+                if not res:
+                    m = 1
+                else:
+                    m = res[-1] + 1
+                for i in range(m, n + 1):
+                    backtrace(res + [i])
+
+        backtrace()
+        return results

Python/sln_1_100/test_solution_71_80.py

@@ -2,6 +2,7 @@
 from unittest import TestCase
 from sln_1_100.solution_71_80 import Solution_71_80
 
+
 class TestSolution_71_80(TestCase):
     def setUp(self):
         self.sln = Solution_71_80()
@@ -11,5 +12,9 @@ def test_simplifyPath(self):
         print(ret)
         ret2 = self.sln.simplifyPath('/a/./b///../c/../././../d/..//../e/./f/./g/././//.//h///././/..///')
         print(ret2)
-        self.assertEqual(self.sln.simplifyPath('///'),'/')
+        self.assertEqual(self.sln.simplifyPath('///'), '/')
         self.assertEqual(self.sln.simplifyPath('/...'), '/...')
+
+    def test_combine(self):
+        ret = self.sln.combine(4, 2)
+        self.assertEqual(ret, [[1, 2], [1, 3], [1, 4], [2, 3], [2, 4], [3, 4]])