add 203

Author: cch123

S0203-remove-linked-list-elements/Cargo.lock

@@ -0,0 +1,7 @@
+[package]
+name = "S0203-remove-linked-list-elements"
+version = "0.1.0"
+authors = ["xargin <cao1988228@163.com>"]
+edition = "2018"
+
+[dependencies]

S0203-remove-linked-list-elements/Cargo.toml

@@ -0,0 +1,85 @@
+fn main() {
+    println!("Hello, world!");
+}
+
+// Definition for singly-linked list.
+ #[derive(PartialEq, Eq, Debug)]
+ pub struct ListNode {
+   pub val: i32,
+   pub next: Option<Box<ListNode>>
+ }
+
+ impl ListNode {
+   #[inline]
+   fn new(val: i32) -> Self {
+     ListNode {
+       next: None,
+       val
+     }
+   }
+ }
+
+struct Solution;
+
+impl Solution {
+    pub fn remove_elements(mut head: Option<Box<ListNode>>, val: i32) -> Option<Box<ListNode>> {
+        while head.is_some() && head.as_ref().unwrap().val == val {
+            head = head.unwrap().next;
+        }
+        if head.is_none() {
+            return head
+        }
+
+        let mut cur = &mut head;
+        while cur.as_ref().unwrap().next.is_some() {
+            if cur.as_ref().unwrap().next.as_ref().unwrap().val == val {
+                let next= std::mem::replace(&mut cur.as_mut().unwrap().next, None);
+                std::mem::replace(&mut cur.as_mut().unwrap().next, next.unwrap().next);
+                continue;
+            }
+            cur = &mut cur.as_mut().unwrap().next;
+        }
+
+        return head;
+    }
+}
+
+/*
+use std::mem;
+impl Solution {
+    pub fn remove_elements(mut head: Option<Box<ListNode>>, val: i32) -> Option<Box<ListNode>> {
+        let mut cur = &mut head;
+        while cur.is_some() {
+            match cur.as_ref() {
+                Some(node) if node.val == val => {
+                    let mut move_out = cur.take();
+                    mem::swap(cur, &mut move_out.as_mut().unwrap().next);
+                    continue;
+                }
+                _ => {}
+            }
+            cur = &mut cur.as_mut().unwrap().next;
+        }
+        head
+    }
+}
+*/
+
+/*
+这个很优雅
+impl Solution {
+    pub fn remove_elements(head: Option<Box<ListNode>>, val: i32) -> Option<Box<ListNode>> {
+        let mut dummy = ListNode{val:0, next:head};
+        let mut p = &mut dummy;
+        while let Some(q) = p.next.as_mut() {
+            if q.val == val {
+                p.next = q.next.take();
+            }else{
+                p = p.next.as_mut().unwrap();
+            }
+        }
+
+        dummy.next
+    }
+}
+*/