Rust revese List

I want to build palindrom checker in Rust, the constraint is O(n) time with 0(1) additional space. My ideas are:

1. Get the middle of the linked list.

2. Reverse the second half of the linked list.

3. Check if the first half and second half are identical.

   fn isListPalindrome(l: ListNode<i32>) -> bool {       let mut fastPointer = &l;     let mut slowPointer = &l;     let mut midIndex = 0;       // here first step         loop {         match fastPointer {             Some(n) => {                 if let Some(nn) = &n.next {                   fastPointer = &nn.next;                 } else {                     break;                 }                 midIndex += 1;                 },             None => break         }         match slowPointer {             Some(n) => {                 slowPointer = &n.next             },             None => break         }     }       if let Some(_fp) = &fastPointer {         slowPointer = &fastPointer;     }       // here is second step to reverse list     let mut prev = None;     while let Some(n) = slowPointer {         let next = &n.next;         n.next = prev.take();         println!("{:?}", n);         prev = &n;         slowPointer = next;     }     true   }  

   but got error

   note: expected reference &std::option::Option<std::boxed::Box<List<i32>>> found reference &&std::boxed::Box<List<i32>>

How to reverse list in Rust ? I dont want to create variable list for prev, because it will not make 0(1) additional space

Thanks

https://stackoverflow.com/questions/65769092/rust-revese-list January 18, 2021 at 01:06PM