136. Single Number

Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.

Follow up: Could you implement a solution with a linear runtime complexity and without using extra memory?

 

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.

Rust Solution

struct Solution;

impl Solution {
    fn single_number(nums: Vec<i32>) -> i32 {
        nums.iter().fold(0i32, |res, val| res ^ val)
    }
}

#[test]
fn test() {
    assert_eq!(Solution::single_number(vec![2, 2, 1]), 1);
    assert_eq!(Solution::single_number(vec![4, 1, 2, 1, 2]), 4);
}

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