struct Solution;
impl Solution {
fn array_pair_sum(mut nums: Vec<i32>) -> i32 {
nums.sort_unstable();
nums.chunks(2).fold(0, |sum, pair| sum + pair[0])
}
}
#[test]
fn test() {
let nums = vec![1, 4, 3, 2];
assert_eq!(Solution::array_pair_sum(nums), 4);
}