Binary tree traversal (recursive and non-recursive)

Theory:

1. Recursive definition of first (Root) sequential traversal: If the binary tree is not empty, perform the following operations in sequence: (1) access the root node; (2) traverse the left subtree; (3) traverse the right subtree. 2. recursive algorithm definition for sequential traversal in the middle (Root): If the binary tree is not empty, perform the following operations in sequence: (1) traverse the left subtree; (2) access the root node; (3) traverse the right subtree. 3. recursive algorithm definition after (Root) sequential traversal: If the binary tree is not empty, perform the following operations in sequence: (1) traverse the left subtree; (2) traverse the right subtree; (3) Access the root node

 

JAVA Implementation

Package binary tree; import Java. util. arraylist; import Java. util. using list; import Java. util. list; import Java. util. stack; public class bstree {private list <node> nodelist = new arraylist <node> (); Public node createtree (INT [] A) {for (INT data: a) nodelist. add (new node (data); int lastleftroot =. length/2-1; for (INT I = lastleftroot; I> = 0; I --) {node root = nodelist. get (I); int leftindex = I * 2 + 1; int rightindex = leftind Ex + 1; if (leftindex <. length); {node left = nodelist. get (leftindex); root. setleft (left);} If (rightindex <. length) {node right = nodelist. get (rightindex); root. setrgiht (right) ;}} node root = nodelist. get (0); Return root;} public static void printnode (node) {system. out. print (node. getdata () + "");} public static void preorderstack (node) {stack <node> stack = new stack <node> (); node P = node; If (n Ode! = NULL) {stack. Push (p); While (! Stack. isempty () {node Top = stack. Pop (); printnode (top); If (top. getright ()! = NULL) stack. Push (top. getright (); If (top. getleft ()! = NULL) stack. push (top. getleft () ;}} public static void minorderstack (node) {stack <node> stack = new stack <node> (); node P = node; while (P! = NULL |! Stack. isempty () {While (P! = NULL) {stack. Push (p); P = P. getleft ();} If (! Stack. isempty () {P = stack. pop (); printnode (p); P = P. getright () ;}} public static void postorderstack (node) {stack <node> stack = new stack <node> (); node P = node; node q = P; while (P! = NULL) {While (P. getleft ()! = NULL) {stack. Push (p); P = P. getleft () ;}while (P! = NULL & (P. getright () = NULL | P. getright () = q) {printnode (p); q = P; If (stack. isempty () return; P = stack. pop ();} stack. push (p); P = P. getright () ;}} public static void pretrav (node) {If (node = NULL) return; system. out. print (node. getdata () + ""); pretrav (node. getleft (); pretrav (node. getright ();} public static void midtrav (node) {If (node = NULL) return; midtrav (node. getleft (); system. out. print (node. getdata () + ""); midtrav (node. getright ();} public static void posttrav (node) {If (node = NULL) return; posttrav (node. getleft (); posttrav (node. getright (); system. out. print (node. getdata () + "");} public static void main (string [] ARGs) {// todo auto-generated method stub int [] A =, 16}; // the data is stored in bstree bt = new bstree () based on hierarchical traversal of the binary search tree; node root = BT. createtree (a); pretrav (Root); system. out. println (); preorderstack (Root); system. out. println (); midtrav (Root); system. out. println (); minorderstack (Root); system. out. println (); posttrav (Root); system. out. println (); postorderstack (Root); system. out. println ();}}

 

Binary tree traversal (recursive and non-recursive)