0021-merge-two-sorted-lists.rs

impl Solution {
    pub fn merge_two_lists(list1: Option<Box<ListNode>>, list2: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
        match (list1,list2) {
            (Some(list1),None)=> Some(list1),
            (None,Some(list2))=>Some(list2),
            (None,None)=>None,
            (Some(l1),Some(l2))=>{
                if l1.val<l2.val {
                  return Some(Box::new(ListNode{val:l1.val,next:Solution::merge_two_lists(l1.next,Some(l2))}));
                }else {
                  return Some(Box::new(ListNode { val: l2.val, next: Solution::merge_two_lists(Some(l1),l2.next) }))
                }
            }
        }
    }
}