217_Contains_Duplicate

219_Contains_Duplicate_II
220_Contains_Duplicate_III

Author: qiyuangong

README.md

@@ -66,4 +66,7 @@
 | 166 | [Fraction to Recurring Decimal](https://leetcode.com/problems/fraction-to-recurring-decimal/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/166_Fraction_to_Recurring_Decimal.py) | % and Hash to find duplicate |
 | 167 | [Two Sum II - Input array is sorted](https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/167_Two_Sum_II_Input_array_is_sorted.py) | Two points O(n) and O(1) |
 | 186 | [Reverse Words in a String II](https://leetcode.com/problems/reverse-words-in-a-string-ii/) ♥| [Python](https://github.com/qiyuangong/leetcode/blob/master/python/186_Reverse_Words_in_a_String_II.py) | Reverse all and reverse each words |
+| 217 | [Contains Duplicate](https://leetcode.com/problems/contains-duplicate/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/217_Contains_Duplicate.py) | 1. Set and compare length<br>2. Sort and check i,i +1|
+| 219 | [Contains Duplicate II](https://leetcode.com/problems/contains-duplicate-ii/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/219_Contains_Duplicate_II.py) | 1. Brute force<br> 2. Maintenance a set that contains previous k numbers, and check if curr in set |
+| 220 | [Contains Duplicate III](https://leetcode.com/problems/contains-duplicate-iii/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/220_Contains_Duplicate_III.py) | 1. Sort and binary Search <br>2. Bucket sort |
 | 340 | [Longest Substring with At Most K Distinct Characters](https://leetcode.com/problems/longest-substring-with-at-most-k-distinct-characters/) &hearts; | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/340_Longest_Substring_with_At_Most_K_Distinct_Characters.py) | Maintain a sliding window with at most k distinct characters and a count for this window. Note that the start position need a loop to update.|

python/217_Contains_Duplicate.py

@@ -5,4 +5,11 @@ def containsDuplicate(self, nums):
         :rtype: bool
         """
         # use set to check duplicate
-        return len(nums) != len(set(nums))
+        return len(nums) != len(set(nums))
+
+    # def containsDuplicate(self, nums):
+    #     nums.sort()
+    #     for i in range(len(nums) - 1):
+    #         if nums[i] == nums[i + 1]:
+    #             return True
+    #     return False

python/220_Contains_Duplicate_III.py

@@ -1,3 +1,4 @@
+from collections import OrderedDict
 class Solution(object):
     def containsNearbyAlmostDuplicate(self, nums, k, t):
         """
@@ -6,3 +7,22 @@ def containsNearbyAlmostDuplicate(self, nums, k, t):
         :type t: int
         :rtype: bool
         """
+        # https://discuss.leetcode.com/topic/19991/o-n-python-using-buckets-with-explanation-10-lines
+        # Bucket sort. Each bucket has size of t. For each number, the possible
+        # candidate can only be in the same bucket or the two buckets besides.
+        # Keep as many as k buckets to ensure that the difference is at most k.
+        buckets = {}
+        for i, v in enumerate(nums):
+            # t == 0 is a special case where we only have to check the bucket
+            # that v is in.
+            bucketNum, offset = (v / t, 1) if t else (v, 0)
+            for idx in xrange(bucketNum - offset, bucketNum + offset + 1):
+                if idx in buckets and abs(buckets[idx] - nums[i]) <= t:
+                    return True
+
+            buckets[bucketNum] = nums[i]
+            if len(buckets) > k:
+                # Remove the bucket which is too far away. Beware of zero t.
+                del buckets[nums[i - k] / t if t else nums[i - k]]
+
+        return False