95 lines
1.6 KiB
Markdown
95 lines
1.6 KiB
Markdown
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# Leetcode Single-Number
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#### 2022-07-22 15:31
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> ##### Algorithms:
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>
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> #algorithm #bit_manipulation
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>
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> ##### Data structures:
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>
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> #DS #bitset
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>
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> ##### Difficulty:
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>
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> #coding_problems #difficulty_easy
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>
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> ##### Additional tags:
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>
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> #leetcode
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>
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> ##### Revisions:
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>
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> N/A
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##### Related topics:
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##### Links:
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- [Link to problem](https://leetcode.com/problems/single-number/)
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- [Learn about XOR](https://en.wikipedia.org/wiki/Exclusive_or#Computer_science)
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- [Explanation](https://leetcode.com/problems/single-number/discuss/1772139/C%2B%2Bor-Explained-Everything-w-WHY-XOR-WORKSor-BRUTE-FORCE-TO-OPTIMIZEDor-STEP-BY-STEP-DRY-RUN)
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***
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### Problem
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Given a **non-empty** array of integers `nums`, every element appears _twice_ except for one. Find that single one.
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You must implement a solution with a linear runtime complexity and use only constant extra space.
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#### Examples
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**Example 1:**
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**Input:** nums = [2,2,1]
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**Output:** 1
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**Example 2:**
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**Input:** nums = [4,1,2,1,2]
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**Output:** 4
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**Example 3:**
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**Input:** nums = [1]
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**Output:** 1
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#### Constraints
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- `1 <= nums.length <= 3 * 104`
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- `-3 * 104 <= nums[i] <= 3 * 104`
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- Each element in the array appears twice except for one element which appears only once.
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### Thoughts
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> [!summary]
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> This is a #bit_manipulation problem utilizing the XOR operator
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The XOR operator has some properties:
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```
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a ^ a = 0;
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a ^ b ^ a = a ^ a ^ b = b;
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```
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This can be used for our problem.
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### Solution
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```cpp
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class Solution {
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public:
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int singleNumber(vector<int> &nums) {
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// Using XOR operator
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int ans = 0;
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for (int i : nums) {
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ans ^= i;
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}
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return ans;
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}
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};
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```
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