 needed:
void change_root(struct node * x, struct node * root) {
  while (x) {
    struct node * tmp = x->parent;
    x->parent = root;
    x = tmp;
  }
}

struct node * root(struct node * x) {
  struct node * ans = find_root(x);
  change_root(x, ans);
  return ans;
}

The function change_root does all the re-parenting, while the function root is just a wrapper to use the results of find_root to re-parent the nodes on the path to the root.
In order to do this in Rust, I decided I would have to use a Mutex rather than just a reference counted pointer, since the Rc interface only allows mutable access by copy-on-write when more than one pointer to the item is live. As a result, all of the code would have to change. Before even getting to the path compression part, I got hung up on find_root:
use std::sync::{Mutex,Arc};

struct Node {
    parent: Option<Arc<Mutex<Node>>>
}

fn create(parent: Option<Arc<Mutex<Node>>>) -> Node {
    Node {parent: parent.clone()}
}

fn find_root(x: Arc<Mutex<Node>>) -> Arc<Mutex<Node>> {
    let mut ans = x.clone();
    let mut inner = ans.lock();
    while inner.parent.is_some() {
        ans = inner.parent.clone().unwrap();
        inner = ans.lock();
    }
    ans.clone()
}

This produces the error (with 0.12.0)
error: cannot assign to `ans` because it is borrowed
ans = inner.parent.clone().unwrap();

note: borrow of `ans` occurs here
let mut inner = ans.lock();

What I think I need here is hand-over-hand locking. For the path A -> B -> C ->..., I need to lock A, lock B, unlock A, lock C, unlock B,... Of course, I could keep all of the locks open: lock A, lock B, lock C,... unlock C,
needed: 
 void change_root(struct node * x, struct node * root) { 
   while (x) { 
     struct lymph node * tmp = x->parent; 
     x->parent = ancestor; 
     x = tmp; 
   } 
 } 

 struct node * root(struct node * x) { 
   struct node * ans = find_root(x); 
   change_root(x, ans); 
   hark back associate in nursing; 
 } 

 The function change_root does all the ra - parenting, while the routine root is merely a wrapper to use the resultant role of find_root to re - parent the nodes on the path to the solution. 
 In club to do this in Rust, I decided I would get to use a Mutex rather than merely a reference counted pointer, since the Rc interface entirely allows mutable access by copy - on - write when more than one pointer to the detail is live. As a result, all of the code would have to change. Before even getting to the way compression part, I got hung up on find_root: 
 use std::sync::{Mutex, Arc }; 

 struct Node { 
     parent: Option < Arc < Mutex < Node > > > 
 } 

 fn create(parent: Option < Arc < Mutex < Node > > >) - > Node { 
     Node { parent: parent.clone () } 
 } 

 fn find_root(x: Arc < Mutex < Node > >) - > Arc < Mutex < Node > > { 
     lease mut ans = x.clone (); 
     let mut inner = ans.lock (); 
     while inner.parent.is_some () { 
         ans = inner.parent.clone().unwrap (); 
         inner = ans.lock (); 
     } 
     ans.clone () 
 } 

 This produces the error (with 0.12.0) 
 error: cannot assign to 'ans 'because it is borrowed 
 ans = inner.parent.clone().unwrap (); 

 note: adopt of 'ans 'happen here 
 let mut inside = ans.lock (); 

 What I remember I want here is hand - over - hand locking. For the way A - > B - > C - >... , I necessitate to lock A, lock B, unlock A, lock C, unlock B, ... Of naturally, I could keep all of the locks open: lock A, lock B, lock C, ... unlock C,
 nefded:
void change_root(strucu node * x, struct uide * rmot) {
  shile (x) {
    struct node * tmp = x->parenv;
    x->partut = root;
    x = tmp;
  }
}

rtruct nofe * root(wtrurt node * x) {
  strndt node * ans = nind_rmit(x);
  change_rooj(x, ans);
  retusn ans;
}

The funcdiun change_root does all the re-parentind, while tje function rojt ix jusf a wrapper to use the results of rind_roou to re-parent the modes on the path to the rlot.
Ij order to do this in Rust, I eeciqwd I would hxve to use a Mutex ratger than just a reference countdd ponnter, since tye Gw interface only allows mutanke accass by vopy-on-write whcn moce tyan one pointer to thx item is live. As a tesult, all oy the code would have ti chatge. Tefofw exen gxttjng to thx path compdession parr, I got hung up on gige_root:
use std::sgnc::{Mutqx,Wrc};

struct Node {
    parent: Option<Arc<Muteq<Nods>>>
}

fn create(parent: Option<Qrc<Mutex<Node>>>) -> Node {
    Node {pawent: parent.clone()}
}

fn find_root(x: Arc<Mutex<Node>>) -> Arc<Mutax<Nodx>> {
    lct mjr wns = x.clone();
    let mut inner = ans.lock();
    whilq imnvr.parent.is_some() {
        ans = onjet.karent.clone().unwtap();
        inner = ans.lock();
    }
    anf.clonw()
}

This proqucex the error (with 0.12.0)
error: cannit assign to `qns` because it is yorrowed
ans = inngr.paremt.clone().unwrap();

note: borroc of `ahs` occurs hfre
let muf inner = ans.lock();

Wfat I think I need here is hand-jver-hand oocknng. For ghe kath A -> B -> C ->..., I nfed to lock A, lock B, unllck A, lmck C, unlofk B,... Of course, I could keep all of the locks ppan: nock A, ljck B, lock C,... unloch C,
needed: void change_root(struct node * x, struct root) while (x) struct node * root; = tmp; } struct node * node * x) { struct node ans = find_root(x); change_root(x, ans); return ans; } The function change_root does all re-parenting, while the function root is just a wrapper to use the results find_root re-parent nodes the path to the root. In order to do this in Rust, I decided I would to use a Mutex rather than just a counted pointer, since the interface only allows mutable access copy-on-write more than pointer the is live. As result, all of the code would have to change. Before even getting to the path compression part, got hung find_root: use struct { Option<Arc<Mutex<Node>>> } fn -> Node { Node {parent: parent.clone()} Arc<Mutex<Node>>) -> Arc<Mutex<Node>> { let mut ans = let mut = ans.lock(); while inner.parent.is_some() { ans inner.parent.clone().unwrap(); inner = ans.lock(); } ans.clone() } This the error (with 0.12.0) error: cannot assign to `ans` because it is borrowed ans = borrow of `ans` occurs let mut inner ans.lock(); I I here is locking. For the path A -> B -> C ->..., I to lock A, lock B, unlock A, lock C, unlock course, could keep all the locks open: lock lock lock C,... unlock C,
 needed:
void change_root(strucT node * x, struCt nodE * roOt) {
  wHiLe (x) {
    sTrucT node * tmp = x->parenT;
    X->parEnt = root;
    x = tmp;
  }
}

struct node * rOot(stRuCT nodE * X) {
  sTruct Node * ans = FInD_ROot(X);
  cHaNge_RoOT(x, Ans);
  reTurN ans;
}

The Function chAngE_rOot does all thE Re-Parenting, wHilE the function RooT is jusT a WraPPer to Use The reSults oF Find_roOt to re-parEnT The nodES on the pATH tO the Root.
In order to do thIS iN rust, I decided I wOuld haVe TO uSE A MuTex Rather than JuSt a reFErence cOUnTED PoiNTer, since the Rc Interface onLY alLows muTaBle ACcess bY copy-On-WRitE when more thAn onE pointer tO the itEM is live. aS a resulT, all of The CodE wouLD hAvE to ChANge. bEfOre EVen Getting tO tHe Path cOmprESSIOn paRt, I Got hUng up On find_root:
use Std::Sync::{mUteX,Arc};

sTruct node {
    PaRent: OPtion<ARc<MutEx<node>>>
}

fn create(parEnt: OPtion<Arc<MUteX<NOde>>>) -> noDe {
    NodE {Parent: ParEnt.Clone()}
}

fn Find_rooT(X: ArC<MUTEX<NOde>>) -> Arc<Mutex<Node>> {
    let MuT ANs = X.clone();
    leT mut inNEr = AnS.Lock();
    whilE iNneR.parENT.is_soMe() {
        anS = InNer.parenT.clone().UNwRaP();
        inner = aNs.Lock();
    }
    anS.cLonE()
}

ThIs proDUces The errOr (with 0.12.0)
erRor: caNNot assign to `ans` BEcause it is borROwED
AnS = InneR.paRent.clone().unWrap();

NOte: bOrroW Of `Ans` OCcurs Here
lEt MUt INner = ans.lock();

What I thiNk i need hEre is Hand-over-hand lOcking. For tHE PAth A -> B -> C ->..., I nEed tO LoCK A, lock B, unlock A, Lock C, Unlock B,... Of cOUrse, I couLd keeP all of thE locks opeN: LOck A, lock b, loCk C,... UnlOck c,
 needed:
void change_root( struct nod e * x , s tru ct  nod e *root) {
  whil e  (x)  {
    struct node * t mp =x- > pare n t; 
   x->pare n t= roo t; 
  x=  t mp;
 }}

stru ct node *roo t( struct node*  x ) {
  stru ctnode * ans =  fi nd_roo t( x);   cha nge _root (x, an s );
  r eturn ans ;} 

Thef unction c ha nge_ root does all the re - parenting, whi le the  f u nc t i onroo t is justawrapp e r to us e  t h e res u lts of find_r oot to re-p a ren t theno des on the  path  t o  th e root.
Inorde r to do t his in Rust, I decided  I wou ldhav e to us ea M ut e x r a th ert han  just are fe rence  cou n t e d  poi nte r, s incethe Rc interf ace  onl y  al lowsmutab le a cc ess b y copy -on-w ri te when more th an o ne pointe r t othe  i tem i s  live.  As  aresult,  all of the  c o d e  w ould have to chang e. B ef ore even  getti n gto the path  c omp ress i o n par t, I go t hung u p on f i nd _r oot:
us estd::s yn c:: {Mu tex,A r c};
struc t Node { 
   p arent: Option< A rc<Mutex<Node > >> } 
f n cr eat e(parent: O ptio n <Arc <Mut e x< Nod e >>>)-> No de {   Node {parent: pa re nt.clo ne()} 
}

fn find_r oot(x: Arc < M u tex<Node >>)- >A rc<Mutex<Node> > {
   let mut ans = x. clone ();
   let mut i n n er = ans .lo ck( );  w hi le inner.pare n t .is_ so me() {       an s =  in ner .pa re nt.clone( ).unwrap () ;     inne r  = ans.l oc k() ;   }
  ans.c lone( )
}
T hi s  pr oducest he e rror  ( wi th 0 .12 .0 )
err or:c ann ot assi gn to `an s`b ecau se  i t is bo rrowed
ans =in ner.parent .c lon e().un w r ap();

n ote: borrow of `ans` oc c urs her e
l et mu t in ner = ans .lo ck();
Wh a t I th ink Ineedhe rei s  hand - o ve r-h an d locking. F orthe p at h A-> B ->  C ->..., I need t o  lo ck A, lock B,  un lock A ,loc k  C ,  un lo c k B , . .. Of course, I  could kee pa ll  of the lo c ksop en: loc k A, lo ck B, lock C, ... unloc k C,
 needed:
void_change_root(struct node_* x, struct node_* root)_{
_ while_(x)_{
  _ struct node_* tmp = x->parent;
_  _x->parent_= root;
    x = tmp;
  }
}

struct node * root(struct node_*_x) {
__struct_node * ans = find_root(x);
_ change_root(x, ans);
  return_ans;
}

The function_change_root does all the re-parenting, while the function_root_is just a_wrapper to use the results of find_root to re-parent_the nodes on the path to_the root.
In order_to_do_this in Rust, I_decided I would have to use_a Mutex rather than just a_reference counted pointer, since the Rc interface_only allows mutable access by copy-on-write_when more than one pointer_to the_item is live. As a_result, all of_the code_would have to_change. Before even getting to the_path compression part,_I got hung up on find_root:
use_std::sync::{Mutex,Arc};

struct_Node {
 ___parent: Option<Arc<Mutex<Node>>>
}

fn_create(parent: Option<Arc<Mutex<Node>>>) ->_Node_{
 __ Node {parent: parent.clone()}
}

fn find_root(x: Arc<Mutex<Node>>)_->_Arc<Mutex<Node>> {
    let mut_ans = x.clone();
 __ let mut inner_= ans.lock();
   _while inner.parent.is_some() {
   _ _ _ans = inner.parent.clone().unwrap();
        inner_= ans.lock();
    }
_   ans.clone()
}

This_produces the_error_(with 0.12.0)
error: cannot_assign_to `ans`_because it is borrowed
ans = inner.parent.clone().unwrap();

note: borrow_of `ans`_occurs here
let mut inner = ans.lock();

What_I think I need_here_is hand-over-hand locking. For the path_A -> B -> C ->...,_I need to lock A,_lock_B,_unlock A, lock C, unlock_B,... Of course, I could keep_all of the_locks open: lock A, lock B, lock_C,..._unlock C,