#![allow(dead_code)]
// Problem solving by checksum
pub fn single_number(nums: Vec<i32>) -> i32 {
let mut res = 0;
for num in &nums {
res ^= num;
}
res
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test1() {
let nums = vec![4, 1, 2, 1, 2];
assert_eq!(single_number(nums), 4);
}
}