Solutions for problem similar to binary search, array

Author: Garvit244

400-500Q/442.py

@@ -0,0 +1,31 @@
+'''
+Given an array of integers, 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.
+
+Find all the elements that appear twice in this array.
+
+Could you do it without extra space and in O(n) runtime?
+
+Example:
+Input:
+[4,3,2,7,8,2,3,1]
+
+Output:
+[2,3]
+'''
+
+class Solution(object):
+    def findDuplicates(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: List[int]
+        """
+        if not nums:
+            return []
+        
+        result = []
+        for _, num in enumerate(nums):
+            index = abs(num)-1
+            if nums[index] < 0:
+                result.append(index+1)
+            nums[index]*=-1
+        return result

400-500Q/448.py

@@ -0,0 +1,33 @@
+'''
+Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.
+
+Find all the elements of [1, n] inclusive that do not appear in this array.
+
+Could you do it without extra space and in O(n) runtime? You may assume the returned list does not count as extra space.
+
+Example:
+
+Input:
+[4,3,2,7,8,2,3,1]
+
+Output:
+[5,6]
+'''
+
+class Solution(object):
+    def findDisappearedNumbers(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: List[int]
+        """
+        if not nums:
+            return []
+        result = []
+        for num in nums:
+            index = abs(num)-1
+            if nums[index] > 0:
+                nums[index]*=-1
+        for index, num in enumerate(nums):
+            if num >0:
+                result.append(index+1)
+        return result

README.md

@@ -89,6 +89,8 @@ Python solution of problems from [LeetCode](https://leetcode.com/).
 | # | Title | Solution | Difficulty |
 |---| ----- | -------- | ---------- |
 |454|[4Sum II](https://leetcode.com/problems/4sum-ii/)|[Python](./400-500Q/454.py)|Medium|
+|448|[Find All Numbers Disappeared in an Array](https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array)|[Python](./400-500q/448.py)|Easy|
+|442|[Find All Duplicates in an Array](https://leetcode.com/problems/find-all-duplicates-in-an-array)|[Python](./400-500q/442.py)|Easy|
 |410|[Split Array Largest Sum](https://leetcode.com/problems/split-array-largest-sum/) | [Python](./400-500Q/410.py)|Hard|