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【遍历二叉树】06二叉树曲折(Z字形)层次遍历II【Binary Tree Zigzag Level Order Traversal】

2014-04-08 16:44 525 查看

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++给定一个二叉树，返回他的Z字形层次遍历的节点的values。(提示，从左到右，然后下一层从右到左，然后再变化方向，就是这样一层一层的遍历)例如：给定一个二叉树

{3,9,20,#,#,15,7}

返回的层次遍历的结果是：

[
[3],
[20,9],
[15,7]
]

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right to left for the next level and alternate between).For example:
Given binary tree

{3,9,20,#,#,15,7}

return its zigzag level order traversal as:

[
[3],
[20,9],
[15,7]
]

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

test.cpp：

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#include <iostream>
#include <cstdio>
#include <stack>
#include <vector>
#include "BinaryTree.h"using namespace std;/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
vector<vector<int> > zigzagLevelOrder(TreeNode *root)
{
vector<vector<int> > matrix;
if(root == NULL)
{
return matrix;
}vector<int> temp;
temp.push_back(root->val);
matrix.push_back(temp);vector<TreeNode *> path;
path.push_back(root);int count = 1;
/*拨动开关-因为第二次是从右边到左边*/
bool lefttoright = false;while(!path.empty())
{
TreeNode *tp = path.front();
if(tp->left != NULL)
{
path.push_back(tp->left);
}
if(tp->right != NULL)
{
path.push_back(tp->right);
}path.erase(path.begin());
count--;if(count == 0 && path.size())
{
vector<int> tmp;
tmp.clear();
if(lefttoright)
{
/*从左到右*/
vector<TreeNode *>::iterator it = path.begin();
for(; it != path.end(); ++it)
{
tmp.push_back( (*it)->val );
}
lefttoright = false;
}
else
{
/*从右到左-下面这段代码VS运行错误不知道为什么*/
//vector<TreeNode *>::iterator it = path.end();
//for(--it; it >= path.begin(); --it)
//{
// tmp.push_back( (*it)->val );
//}
for (int i = path.size() - 1; i >= 0; --i)
{
tmp.push_back( path[i]->val );
}lefttoright = true;
}
matrix.push_back(tmp);
count = path.size();
}
}
return matrix;
}// 树中结点含有分叉，
// 8
// / \
// 6 1
// / \
// 9 2
// / \
// 4 7
int main()
{
TreeNode *pNodeA1 = CreateBinaryTreeNode(8);
TreeNode *pNodeA2 = CreateBinaryTreeNode(6);
TreeNode *pNodeA3 = CreateBinaryTreeNode(1);
TreeNode *pNodeA4 = CreateBinaryTreeNode(9);
TreeNode *pNodeA5 = CreateBinaryTreeNode(2);
TreeNode *pNodeA6 = CreateBinaryTreeNode(4);
TreeNode *pNodeA7 = CreateBinaryTreeNode(7);ConnectTreeNodes(pNodeA1, pNodeA2, pNodeA3);
ConnectTreeNodes(pNodeA2, pNodeA4, pNodeA5);
ConnectTreeNodes(pNodeA5, pNodeA6, pNodeA7);PrintTree(pNodeA1);vector<vector<int> > ans = zigzagLevelOrder(pNodeA1);for (int i = 0; i < ans.size(); ++i)
{
for (int j = 0; j < ans[i].size(); ++j)
{
cout << ans[i][j] << " ";
}
cout << endl;
}DestroyTree(pNodeA1);
return 0;
}

输出结果：

题目ac了，但是测试用例没有通过

BinaryTree.h:

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#ifndef _BINARY_TREE_H_
#define _BINARY_TREE_H_struct TreeNode
{
int val;
TreeNode *left;
TreeNode *right;
TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};TreeNode *CreateBinaryTreeNode(int value);
void ConnectTreeNodes(TreeNode *pParent,
TreeNode *pLeft, TreeNode *pRight);
void PrintTreeNode(TreeNode *pNode);
void PrintTree(TreeNode *pRoot);
void DestroyTree(TreeNode *pRoot);#endif /*_BINARY_TREE_H_*/

BinaryTree.cpp:

#include <iostream>
#include <cstdio>
#include "BinaryTree.h"using namespace std;/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*///创建结点
TreeNode *CreateBinaryTreeNode(int value)
{
TreeNode *pNode = new TreeNode(value);return pNode;
}//连接结点
void ConnectTreeNodes(TreeNode *pParent, TreeNode *pLeft, TreeNode *pRight)
{
if(pParent != NULL)
{
pParent->left = pLeft;
pParent->right = pRight;
}
}//打印节点内容以及左右子结点内容
void PrintTreeNode(TreeNode *pNode)
{
if(pNode != NULL)
{
printf("value of this node is: %d\n", pNode->val);if(pNode->left != NULL)
printf("value of its left child is: %d.\n", pNode->left->val);
else
printf("left child is null.\n");if(pNode->right != NULL)
printf("value of its right child is: %d.\n", pNode->right->val);
else
printf("right child is null.\n");
}
else
{
printf("this node is null.\n");
}printf("\n");
}//前序遍历递归方法打印结点内容
void PrintTree(TreeNode *pRoot)
{
PrintTreeNode(pRoot);if(pRoot != NULL)
{
if(pRoot->left != NULL)
PrintTree(pRoot->left);if(pRoot->right != NULL)
PrintTree(pRoot->right);
}
}void DestroyTree(TreeNode *pRoot)
{
if(pRoot != NULL)
{
TreeNode *pLeft = pRoot->left;
TreeNode *pRight = pRoot->right;delete pRoot;
pRoot = NULL;DestroyTree(pLeft);
DestroyTree(pRight);
}
}

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