algorithms-python/algorithms/bit/find_difference.py at master · Mu-L/algorithms-python · GitHub

28 lines (25 loc) · 747 Bytes

"""

Given two strings s and t which consist of only lowercase letters.

String t is generated by random shuffling string s and then add one more letter

at a random position. Find the letter that was added in t.

For example:

Input:

s = "abcd"

t = "abecd"

Output: 'e'

Explanation:

'e' is the letter that was added.

"""

We use the characteristic equation of XOR.

A xor B xor C = A xor C xor B

If A == C, then A xor C = 0

and then, B xor 0 = B

"""

def find_difference(s, t):

ret = 0

for ch in s + t:

# ord(ch) return an integer representing the Unicode code point of that character

ret = ret ^ ord(ch)

# chr(i) Return the string representing a character whose Unicode code point is the integer i

return chr(ret)

Expand file tree