add 206

Author: cch123

S0206-reverse-linked-list/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "S0206-reverse-linked-list"
+version = "0.1.0"
+authors = ["xargin <cao1988228@163.com>"]
+edition = "2018"
+
+[dependencies]
+leetcode_prelude="0.1"

S0206-reverse-linked-list/src/main.rs

@@ -0,0 +1,42 @@
+use leetcode_prelude::*;
+fn main() {
+    let l = linkedlist![1,2,3,4];
+    println!("{:?}", Solution::reverse_list(l));
+}
+
+impl Solution {
+    pub fn reverse_list(mut head: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
+        let cur = &mut head;
+        let mut prev = None;
+        while cur.is_some() {
+            let mut cur_next = std::mem::replace(&mut cur.as_mut().unwrap().next, prev.take());
+            prev = cur.take();
+            std::mem::swap(&mut cur_next, cur);
+        }
+
+        prev
+    }
+}
+struct Solution;
+
+/*
+impl Solution {
+    pub fn reverse_list(head: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
+        let mut head = head; //move
+        let mut new_head:Option<Box<ListNode>> = None;
+        loop {
+            if head.is_none() {
+                break;
+            }
+            let val = head.as_mut().unwrap().val;
+            let mut new_node = ListNode::new(val);
+            if new_head.is_some() {
+                new_node.next = new_head;
+            }
+            new_head = Some(Box::new(new_node));
+            head = head.unwrap().next;
+        }
+        new_head
+    }
+}
+*/