在二元树中找出和为某一值的所有路径

    具体实现代码如下：

BSTree.h具体内容：

#ifndef _BSTREE_H_
#define _BSTREE_H_
typedef struct _tagBSTreeNode
{
	int m_nVal;
	_tagBSTreeNode * m_pLeft;
	_tagBSTreeNode * m_pRight;
}BSTreeNode;
extern BSTreeNode * pHead;
//追加树结点
int AppendNode(BSTreeNode **, int nNum);
//打印树结点
void PrintTree(BSTreeNode ** ppTree);
//释放树
void Clear(BSTreeNode ** ppTree);
//转换为有序双链表
void InOrderTree(BSTreeNode ** ppTree);
//销毁链表
void ClearList(BSTreeNode * pHead);
//打印链表
void PrintList(BSTreeNode * pHead);
//打印路径
void PrintPath(BSTreeNode * pHead, int nSum);
//打印和路径
void PrintSumPath(BSTreeNode ** ppTree, int nLayer, int nPathSum);
#endif

BSTree.cpp的内容：

#include <stdlib.h>
#include <stdio.h>
#include "BSTree.h"

//追加树结点
int AppendNode(BSTreeNode ** ppTree, int nNum)
{
	BSTreeNode * pNewNode = NULL;
	if (!ppTree)
		return 0;
	if (*ppTree == NULL)
	{
		pNewNode = (BSTreeNode *)malloc(sizeof(BSTreeNode));
		if (!pNewNode)
			return 0;
		pNewNode->m_nVal = nNum;
		pNewNode->m_pLeft = NULL;
		pNewNode->m_pRight = NULL;
		*ppTree = pNewNode;
		return 1;
	}
	if ((*ppTree)->m_nVal > nNum)
	{
		AppendNode(&((*ppTree)->m_pLeft), nNum);
	}
	else if ((*ppTree)->m_nVal < nNum)
	{
		AppendNode(&((*ppTree)->m_pRight), nNum);
	}
	else
	{
		printf("树结点已经存在.\n");
		return 0;
	}
	return 1;
}
//打印树结点
void PrintTree(BSTreeNode ** ppTree)
{
	if (!ppTree)
		return;
	if (*ppTree == NULL)
	{
		return;
	}
	if ((*ppTree)->m_pLeft)
		PrintTree(&((*ppTree)->m_pLeft));
	if (*ppTree)
		printf("%d", (*ppTree)->m_nVal);
	if ((*ppTree)->m_pRight)
		PrintTree(&((*ppTree)->m_pRight));
}

//释放树
void Clear(BSTreeNode ** ppTree)
{
	BSTreeNode * pLeftTree = NULL;
	BSTreeNode * pRightTree = NULL;
	if (!ppTree)
		return;
	if (*ppTree == NULL)
		return;
	if ((*ppTree)->m_pLeft)
	{
		pLeftTree = (*ppTree)->m_pLeft;
		Clear(&pLeftTree);
	}
	if ((*ppTree)->m_pRight)
	{
		pRightTree = (*ppTree)->m_pRight;
		Clear(&pRightTree);
	}
	if (*ppTree)
	{
		free(*ppTree);
		*ppTree = NULL;
	}
	return;
}

//以左孩子为前驱
//以右孩子为后继
BSTreeNode * pHead = NULL;

void AppendNode2List(BSTreeNode * pInput)
{
	BSTreeNode * pCurNode = NULL;
	if (pInput == NULL)
		return;
	if (!pHead)
	{
		pHead = pInput;
		pInput->m_pLeft = NULL;
		pInput->m_pRight = NULL;
		return;
	}
	pCurNode = pHead;
	while (pCurNode->m_pRight)
	{
		pCurNode = pCurNode->m_pRight;
	}
	pCurNode->m_pRight = pInput;
	pInput->m_pLeft = pCurNode;
	pInput->m_pRight = NULL;
	return ;
}

//打印树结点
void InOrderTree(BSTreeNode ** ppTree)
{
	if (!ppTree)
		return;
	if (*ppTree == NULL)
	{
		return;
	}
	if ((*ppTree)->m_pLeft)
		InOrderTree(&((*ppTree)->m_pLeft));
	if (*ppTree)
		AppendNode2List(*ppTree);
	if ((*ppTree)->m_pRight)
		InOrderTree(&((*ppTree)->m_pRight));
}

void PrintList(BSTreeNode * pHead)
{
	BSTreeNode * pCurNode = NULL;
	if (!pHead)
		return;
	pCurNode = pHead;
	printf("\n链表数据：\n");
	while (pCurNode)
	{
		printf("%d	", pCurNode->m_nVal);
		pCurNode = pCurNode->m_pRight;
	}
	return;
}

void ClearList(BSTreeNode * pHead)
{
	BSTreeNode * pCurNode = NULL;
	if (!pHead)
		return;
	while (pHead)
	{
		pCurNode = pHead->m_pRight;
		free(pHead);
		pHead = pCurNode;
	}
	return;
}

//打印和路径
void PrintSumPath(BSTreeNode ** ppTree, int nLayer, int nPathSum)
{
	static int Sum[256] = { 0 };
	int nSum = 0;
	int i = 0;
	if (!ppTree)
		return;
	if (*ppTree == NULL)
	{
		return;
	}
	if (*ppTree)
	{
		Sum[nLayer] = (*ppTree)->m_nVal;
	}	
	if ((*ppTree)->m_pLeft)
		PrintSumPath(&((*ppTree)->m_pLeft), nLayer + 1, nPathSum);
	if ((*ppTree)->m_pRight)
		PrintSumPath(&((*ppTree)->m_pRight), nLayer + 1, nPathSum);
	if (((*ppTree)->m_pLeft==NULL) && ((*ppTree)->m_pRight == NULL))
	{
		for (i = 0; i <= nLayer; i++)
		{
			nSum += Sum[i];			
		}
		if (nSum == nPathSum)
		{
			printf("路径：\n");
			for (i = 0; i <= nLayer; i++)
			{
				printf("%d	", Sum[i]);
			}
			printf("\n");
		}
	}
	return;
}

main.cpp的内容：

#define _CRTDBG_MAP_ALLOC
#include <stdlib.h>
#include <stdio.h>
#include <crtdbg.h>
#include "BSTree.h"

void main()
{
	BSTreeNode * pTree = NULL;
	if (AppendNode(&pTree, 10) == NULL)
	{
		printf("追加失败.\n");
		return;
	}
	if (AppendNode(&pTree, 5) == NULL)
	{
		printf("追加失败.\n");
		return;
	}
	if (AppendNode(&pTree, 12) == NULL)
	{
		printf("追加失败.\n");
		return;
	}
	if (AppendNode(&pTree, 4) == NULL)
	{
		printf("追加失败.\n");
		return;
	}
	if (AppendNode(&pTree, 7) == NULL)
	{
		printf("追加失败.\n");
		return;
	}
	PrintTree(&pTree);
	PrintSumPath(&pTree, 0,22); //找出和为22的值
	Clear(&pTree);
	_CrtDumpMemoryLeaks();
	system("pause");
	return;
}

运行效果如图1所示：

图1 运行效果