Merge pull request keon#57 from ofek/add-find-missing-number

add find_missing_number

Author: ankit167

README.md

@@ -40,6 +40,7 @@ Minimal and clean example implementations of data structures and algorithms in P
 - [bit](bit)
     - [bytes_int_conversion](bit/bytes_int_conversion.py)
     - [count_ones](bit/count_ones.py)
+    - [find_missing_number](bit/find_missing_number.py)
     - [power_of_two](bit/power_of_two.py)
     - [reverse_bits](bit/reverse_bits.py)
     - [single_number2](bit/single_number2.py)

bit/find_missing_number.py

@@ -0,0 +1,18 @@
+def find_missing_number(nums):
+    """Returns the missing number from a sequence of unique integers
+    in range [0..n] in O(n) time and space. The difference between
+    consecutive integers cannot be more than 1. If the sequence is
+    already complete, the next integer in the sequence will be returned.
+
+    >>> find_missing_number(i for i in range(0, 10000) if i != 1234)
+    1234
+    >>> find_missing_number([4, 1, 3, 0, 6, 5, 2])
+    7
+    """
+
+    missing = 0
+    for i, num in enumerate(nums):
+        missing ^= num
+        missing ^= i + 1
+
+    return missing