[First week][contains-duplicate] adds answer

Author: routiful

contains-duplicate/routiful.py

@@ -0,0 +1,37 @@
+# FIRST WEEK
+
+# Question : 217. Contains Duplicate
+# Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.
+
+# Example 1:
+# Input: nums = [1,2,3,1]
+# Output: true
+# Explanation:
+#   The element 1 occurs at the indices 0 and 3.
+
+# Example 2:
+# Input: nums = [1,2,3,4]
+# Output: false
+# Explanation:
+#   All elements are distinct.
+
+# Example 3:
+# Input: nums = [1,1,1,3,3,4,3,2,4,2]
+# Output: true
+
+# Constraints:
+#   1 <= nums.length <= 105
+#   -109 <= nums[i] <= 109 
+
+# Notes:
+# Counts every elements(in the list) using 'count()' API. Luckily it is less than O(n) but maximum O(n)
+# Makes Dict; the key is elements of the list. If the length of them are different, the list has duplicate elements. It is O(n)
+
+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        d = {}
+        for n in nums:
+            d[n] = 1
+        if len(d) != len(nums):
+            return True
+        return False