Add find_all_duplicates.py under correct arrays folder

Author: komalsrivastava282

Python/algorithms/arrays/find_all_duplicates.py

@@ -0,0 +1,19 @@
+"""
+Author: Komal Srivastava
+Time Complexity: O(n)
+Space Complexity: O(1)
+"""
+
+def find_duplicates(nums):
+    res = []
+    for num in nums:
+        index = abs(num) - 1
+        if nums[index] < 0:
+            res.append(abs(num))
+        else:
+            nums[index] *= -1
+    return res
+
+if __name__ == "__main__":
+    sample = [4,3,2,7,8,2,3,1]
+    print("Duplicates:", find_duplicates(sample))