哈弗曼树试验一：构建哈弗曼树HuffmanTree

#include   
#include   
#include   
#include 
using namespace std;
/**
* Definition for binary tree
**/
struct TreeNode {
	int val;
	TreeNode *left;
	TreeNode *right;
	TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

//先序遍历  
void PreOrder(TreeNode *root)
{
	if (root == NULL)
		return;
	std::cout << root->val << ' ';
	PreOrder(root->left);
	PreOrder(root->right);
}

//中序遍历  
void InOrder(TreeNode *root)
{
	if (root == NULL)
		return;
	InOrder(root->left);
	std::cout << root->val << " ";
	InOrder(root->right);
}

//后序遍历  
void PostOrder(TreeNode *root)
{
	if (root == NULL) return;
	PostOrder(root->left);
	PostOrder(root->right);
	std::cout << root->val << ' ';
}

//哈弗曼树结点比较
bool HfCompare(TreeNode *node1, TreeNode *node2)
{
	return node1->val < node2->val;
}
//根据结点序列构建哈弗曼树
TreeNode* ConstructHuffmanTree(vector &treeNodes)
{
	TreeNode *root = NULL;
	if (treeNodes.empty())
		return root;
	while (treeNodes.size() > 1)
	{
		//权值从小到大排序，取最小的两个结点合并
		sort(treeNodes.begin(), treeNodes.end(), HfCompare);
		TreeNode *leftNode = treeNodes[0];
		TreeNode *rightNode = treeNodes[1];
		TreeNode *tempNode = new TreeNode(leftNode->val + rightNode->val);
		tempNode->left = leftNode;
		tempNode->right = rightNode;
		treeNodes.erase(treeNodes.begin());
		treeNodes.erase(treeNodes.begin());
		treeNodes.push_back(tempNode);
		if (treeNodes.size() == 1)
			root = treeNodes[0];
	}
	return root;
}

int main()
{
	vector treeNodes;
	int val = 0;
	while (cin >> val)
	{
		TreeNode *tempNode = new TreeNode(val);
		treeNodes.push_back(tempNode);
	}
	TreeNode *root = ConstructHuffmanTree(treeNodes);

	PreOrder(root);    //先序输出  
	std::cout << std::endl;
	InOrder(root);     //中序输出  
	std::cout << std::endl;
	system("pause");
	return 0;
}