update solution: missing-number

Author: dusunax

missing-number/dusunax.py

@@ -3,14 +3,14 @@
 
 A. iterative approach: sort the array and find the missing number.
 B. XOR approach: use XOR to find the missing number.
-  - a ^ a = 0, a ^ 0 = a
+    - a ^ a = 0, a ^ 0 = a
 
 ## Time and Space Complexity
 
 ### A. Iterative Approach
 
 ```
-TC: O(n)
+TC: O(n log n)
 SC: O(1)
 ```
 
@@ -53,13 +53,11 @@ def missingNumberIterative(self, nums: List[int]) -> int:
     '''
     def missingNumberXOR(self, nums: List[int]) -> int:
         n = len(nums)
-        xor_all = 0
         xor_nums = 0
 
         for i in range(n + 1):
-            xor_all ^= i
-        
-        for num in nums:
-            xor_nums ^= num
+            if i < n:
+                xor_nums ^= nums[i]
+            xor_nums ^= i
 
-        return xor_all^xor_nums
+        return xor_nums