136. Single Number
Description
Given a non-empty array of integers nums
, every element appears twice except for one. Find that single one.
You must implement a solution with a linear runtime complexity and use only constant extra space.
Example 1:
Input: nums = [2,2,1] Output: 1
Example 2:
Input: nums = [4,1,2,1,2] Output: 4
Example 3:
Input: nums = [1] Output: 1
Constraints:
1 <= nums.length <= 3 * 104
-3 * 104 <= nums[i] <= 3 * 104
- Each element in the array appears twice except for one element which appears only once.
Solutions
Solution 1: Bitwise Operation
The XOR operation has the following properties:
- Any number XOR 0 is still the original number, i.e., $x \oplus 0 = x$;
- Any number XOR itself is 0, i.e., $x \oplus x = 0$;
Performing XOR operation on all elements in the array will result in the number that only appears once.
The time complexity is $O(n)$, where $n$ is the length of the array. The space complexity is $O(1)$.
1 2 3 |
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1 2 3 4 5 6 7 8 9 |
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1 2 3 4 5 6 7 8 9 10 |
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1 2 3 4 5 6 |
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1 2 3 |
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1 2 3 4 5 |
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1 2 3 4 5 6 7 |
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1 2 3 4 5 |
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1 2 3 4 5 6 7 |
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1 2 3 4 5 |
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Solution 2
1 2 3 4 5 |
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