非递归先,中,后遍历二叉树

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1:后序遍历二叉树

//后序遍历二叉树,在函数中改变了树T,可以在函数中对原树Ｔ进行复制然后处理复制树或者加些辅助结构
public static void InOrderTraverse(Tree T,Tree r){
            Stake<Tree> stake = new Stake<Tree>();//栈
            stake.push(T);
            Tree tem = T;
              
            while(!stake.isEmpty()){
                while(tem!=null && tem.lchild != null){//向左走到尽头,等于访问根的左子树=null
                    stake.push(tem.lchild);
                    tem = tem.lchild;
                }
                  
                tem = tem.rchild;//访问右子树
                if(tem != null)stake.push(tem);
                else{
             //一个节点的左子树和右子树都为null的情况,即表明该根节点的左右子树均已经被访问过了,现在访问根节点
                   tem = stake.pop();
                   System.out.print(tem.ele+" ");//访问根节点
                    
                   tem = stake.peek();
                    
                   if(tem == null) return;//遍历结束
                    
                   if(tem.lchild != null)tem.lchild = null;//如果左子树被访问,设置其左为null，在此处改变了树
                   else tem.rchild = null;//同理,设置其右为null
                }
            }
      }

2:先序和中序遍历二叉树

//非递归方法遍历二叉树,中序遍历

public static void InOrderTraverse(Tree T){

Stake<Tree> stake = new Stake<Tree>();

stake.push(T);

Tree tem = T;

while(!stake.isEmpty()){

while(tem!=null && tem.lchild != null){//向左走到尽头

stake.push(tem.lchild);

tem = tem.lchild;

}

tem = stake.pop();

System.out.print(tem.ele+" ");//访问根节点

tem = tem.rchild;//访问右子树

if(tem != null)stake.push(tem);

}

//非递归方法遍历二叉树二

public static void InOrderTraverse2(Tree T){

Stake<Tree> stake = new Stake<Tree>();//栈道

//stake.push(T);

Tree tem = T;

boolean flag = true;

while(flag || !stake.isEmpty()){

flag = false;

if(tem != null){

System.out.println(tem.ele+" ");//先序遍历法

stake.push(tem); tem = tem.lchild;//遍历左子树

}

else{

tem = stake.pop();

//System.out.print(tem.ele+" ");//中序遍历法访问根节点

tem = tem.rchild;//遍历右子树

}

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