add 61

Author: cch123

S0061-rotate-list/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "S0061-rotate-list"
+version = "0.1.0"
+authors = ["xargin <cao1988228@163.com>"]
+edition = "2018"
+
+[dependencies]

S0061-rotate-list/src/main.rs

@@ -0,0 +1,51 @@
+use leetcode_prelude::*;
+struct Solution;
+
+use std::mem::replace;
+// Definition for singly-linked list.
+impl Solution {
+    pub fn rotate_right(mut head: Option<Box<ListNode>>, k: i32) -> Option<Box<ListNode>> {
+        if head.is_none() || head.as_ref().unwrap().next.is_none() || k == 0 {
+            return head;
+        }
+        let mut cursor = &mut head;
+        // count len
+        let mut len = 0;
+        while cursor.as_ref().is_some() {
+            len += 1;
+            cursor = &mut cursor.as_mut().unwrap().next;
+        }
+
+        let (k, mut cnt) = (len-k % len, 0);
+        cursor = &mut head;
+
+        loop {
+            if cnt == k {
+                let mut target = replace(cursor, None);
+                // find the tail
+                let mut tail = &mut target;
+                while tail.is_some() {
+                    tail = &mut tail.as_mut().unwrap().next;
+                }
+                // now tail is None
+                // replace it to head
+                // set the tail.next = head
+                replace(tail, head);
+                return target;
+            }
+            cursor = &mut cursor.as_mut().unwrap().next;
+            cnt += 1;
+        }
+
+    }
+}
+
+fn main() {
+    let l = linkedlist![1, 2, 3, 4, 5];
+    println!("{:?}", Solution::rotate_right(l, 2));
+    let l = linkedlist![0,1,2];
+    println!("{:?}", Solution::rotate_right(l, 4));
+    let l = linkedlist![1,2];
+    println!("{:?}", Solution::rotate_right(l, 1));
+}
+