剑指offer_把二叉树打印成多行+之字形

/*1. 从上到下按层打印二叉树，同一层结点从左至右输出。每一层输出一行。按层次打印可以用队列，如何保证一层输出一行，进队列的时候，加标记，出队时候遇到标记则一行结束剑指offer思路：用两个变量表示当前层还未打印的节点数和下一层的节点数*/import java.util.ArrayList;import java.util.ArrayDeque;import java.util.Queue;import java.util.Stack;class  Print{public static  ArrayList<ArrayList<Integer>> print1(TreeNode pRoot) {ArrayList<ArrayList<Integer>> alAllLine=new ArrayList<ArrayList<Integer>>();if (pRoot==null){return alAllLine;}ArrayList<Integer> alOneLine=new ArrayList<Integer>();alOneLine.add(pRoot.val);alAllLine.add(alOneLine);Queue<TreeNode> queue=new ArrayDeque<TreeNode>();queue.add(pRoot.left);queue.add(pRoot.right);queue.add(pRoot);//pRoot作为标记ArrayList<Integer> alOneLineNext=new ArrayList<Integer>();while (!queue.isEmpty()){TreeNode front=queue.remove();if (front==pRoot){alAllLine.add(alOneLineNext);if(queue.size()>0){alOneLineNext=new ArrayList<Integer>();queue.add(pRoot);}continue;}alOneLineNext.add(front.val);if (front.left!=null){queue.add(front.left);}if (front.right!=null){queue.add(front.right);}}return alAllLine;    }public static ArrayList<ArrayList<Integer>> print2(TreeNode pRoot){ArrayList<ArrayList<Integer>> alAllLine=new ArrayList<ArrayList<Integer>>();if (pRoot==null){return alAllLine;}int toBePrinted=1;int nextLine=0;Queue<TreeNode> queue=new ArrayDeque<TreeNode>();queue.add(pRoot);ArrayList<Integer> alOneLine=new ArrayList<Integer>();while (!queue.isEmpty()){TreeNode front=queue.remove();alOneLine.add(front.val);toBePrinted--;if (front.left!=null){queue.add(front.left);nextLine++;}if (front.right!=null){queue.add(front.right);nextLine++;}if (toBePrinted==0){alAllLine.add(alOneLine);alOneLine=new ArrayList<Integer>();toBePrinted=nextLine;nextLine=0;}}return alAllLine;}/*2. 请实现一个函数按照之字形打印二叉树，   即第一行按照从左到右的顺序打印，第二层按照从右至左的顺序打印，第三行按照从左到右的顺序打印，其他行以此类推。   如何做到之字，需要栈吗？*/public static  ArrayList<ArrayList<Integer>> printZ(TreeNode pRoot){ArrayList<ArrayList<Integer>> alAllLine=new ArrayList<ArrayList<Integer>>();if (pRoot==null){return alAllLine;}int toBePrinted=1;int nextLine=0;int direct=0;Queue<TreeNode> queue=new ArrayDeque<TreeNode>();queue.add(pRoot);ArrayList<Integer> alOneLine=new ArrayList<Integer>();while (!queue.isEmpty()){TreeNode front=queue.remove();alOneLine.add(front.val);toBePrinted--;if (front.left!=null){queue.add(front.left);nextLine++;}if (front.right!=null){queue.add(front.right);nextLine++;}if (toBePrinted==0){if (direct==0){alAllLine.add(alOneLine);}else//每隔一层进行反转{ArrayList<Integer> alOneLineReverse=new ArrayList<Integer>();for (int i=alOneLine.size()-1; i>=0; i--){alOneLineReverse.add(alOneLine.get(i));}alAllLine.add(alOneLineReverse);}direct=1-direct;alOneLine=new ArrayList<Integer>();toBePrinted=nextLine;nextLine=0;}}return alAllLine;}/*上述方法还是用队列按层次遍历，不过是隔一层利用辅助ArrayList反转一下元素顺序考虑用栈，直接在遍历过程中确定好元素顺序要用两个栈，一个栈用来入，一个用来出，如果只用一个，栈后进先出，元素顺序会打乱*/public static  ArrayList<ArrayList<Integer>> printZ2(TreeNode pRoot){ArrayList<ArrayList<Integer>> alAllLine=new ArrayList<ArrayList<Integer>>();if (pRoot==null){return alAllLine;}Stack<TreeNode> s1=new Stack<TreeNode>();Stack<TreeNode> s2=new Stack<TreeNode>();s1.push(pRoot);while (!s1.empty()||!s2.empty()){ArrayList<Integer> alOneLine=new ArrayList<Integer>();while (!s1.empty()){TreeNode top=s1.pop();alOneLine.add(top.val);if (top.left!=null){s2.push(top.left);}if (top.right!=null){s2.push(top.right);}}if (alOneLine.size()>0){alAllLine.add(alOneLine);}alOneLine=new ArrayList<Integer>();while (!s2.empty()){TreeNode top=s2.pop();alOneLine.add(top.val);if (top.right!=null){s1.push(top.right);}if (top.left!=null){s1.push(top.left);}}if (alOneLine.size()>0){alAllLine.add(alOneLine);}}return alAllLine;}public static void main(String[] args) {TreeNode node1=new TreeNode(1);TreeNode node2=new TreeNode(2);TreeNode node3=new TreeNode(3);TreeNode node4=new TreeNode(4);TreeNode node5=new TreeNode(5);TreeNode node6=new TreeNode(6);TreeNode node7=new TreeNode(7);node1.left=node2;node1.right=node3;node2.left=node4;node2.right=node5;node3.left=node6;node3.right=node7;ArrayList<ArrayList<Integer>> alAllLine=printZ2(node1);for (ArrayList<Integer> alOneLine: alAllLine){for (int i: alOneLine){System.out.print(i);}System.out.println();}}}