Single Number

LeetCode 136 • Easy • Arrays & Hashing

Input: nums = [4,1,2,1,2] → Output: 4. XOR: a^a=0, a^0=a. XOR all numbers; pairs cancel, single remains.

TimeO(n)

SpaceO(1)

i: — res: —

Current

Result (single)

Current —

res —

Speed:

Ready

Press Play. For each n: res ^= n. Pairs cancel (a^a=0), single remains.

Whiteboard

Size:3

Type It

Practice until you don't need to look. XOR: a^a=0, a^0=a.

═══ SINGLE NUMBER — XOR ═══

PATTERN ▸ XOR (a^a=0, a^0=a) O(n) · O(1)

① INIT

res = 0

② LOOP

for n in nums: res ^= n

③ RETURN

return res

your implementation

Verify: