【遍历二叉树】05二叉树的层次遍历II【Binary Tree Level Order Traversal II】


就把vector改成用栈类存放层次遍历的一层的序列

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给定一个二叉树，自底向上的返回他的层次遍历的节点的values。(提示，从左到右，一层一层的遍历，但是这里是从叶子节点到根节点)

例如：

    给定一个二叉树 {3,9,20,#,#,15,7},

    3
   / \
  9  20
    /  \
   15   7

返回的层次遍历的结果是：

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

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Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root).

For example:
Given binary tree {3,9,20,#,#,15,7},

    3
   / \
  9  20
    /  \
   15   7

return its bottom-up level order traversal as:

[
  [15,7]
  [9,20],
  [3],
]
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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> > levelOrderBottom(TreeNode *root)
{

    vector<vector<int> > matrix;
    if(root == NULL)
    {
        return matrix;
    }

    stack<vector<int> > sv;
    vector<int> temp;
    temp.push_back(root->val);
    /*先把根结点的这一行信息放到栈中*/
    sv.push(temp);

    vector<TreeNode *> path;
    path.push_back(root);

    int count = 1;
    while(!path.empty())
    {
        if(path[0]->left != NULL)
        {
            path.push_back(path[0]->left);
        }
        if(path[0]->right != NULL)
        {
            path.push_back(path[0]->right);
        }
        path.erase(path.begin());
        count--;
        if(count == 0)
        {
            vector<int> tmp;
            vector<TreeNode *>::iterator it = path.begin();
            for(; it != path.end(); ++it)
            {
                tmp.push_back((*it)->val);
            }
            sv.push(tmp);
            count = path.size();
        }
    }
    /*遍历结果栈*/
    while(!sv.empty())
    {
        if(sv.top().size() > 0)
        {
            matrix.push_back(sv.top());
        }
        sv.pop();
    }
    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 = levelOrderBottom(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：
4 7 9 2 6 1 8
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:
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#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);
    }
}
posted @ 2014-04-08 16:43  z陵  阅读(206)  评论(0)  编辑  收藏  举报