easy
source: https://leetcode.com/problems/single-number
C/C++ Solution to LeetCode problem 136. Single Number.
Problem
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.
Examples
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.
Solution
From electronics course at university (not a waste of time after all), I know this can be solved using the bitwise XOR operator. Another solution is just to insert each element into a hash table and count how many times appears, there will be only one with counter equal to 1.
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class Solution {
public:
int singleNumber(vector<int>& nums) {
int x = nums[0];
for (int i=1; i<nums.size(); i+=1)
x ^= nums[i];
return x;
}
};