3.9重建二叉树

#include <iostream>

using namespace std;

const int TREELEN=6;

typedef struct NODE
{
    char chVal;
    struct NODE* pLeft;
    struct NODE* pRight;
}NODE;

void rebuild(char *pPreOrder, char *pInOrder, int treeLen, NODE **pRoot)
{
    //前序中序序列为空，返回NULL，失败
    if(pPreOrder == NULL || pInOrder == NULL)
    {
        return ;
    }

    NODE *pTemp =new NODE;
    pTemp->chVal = *pPreOrder;
    pTemp->pLeft = NULL;
    pTemp->pRight = NULL;

    if(*pRoot == NULL)
    {
        *pRoot = pTemp;
    }

    //only have one node return;
    if(treeLen == 1)
    {
        return;
    }

    int tempLen = 0;
    char *leftEnd = pInOrder;

    while(*leftEnd != *pPreOrder)
    {
        if(leftEnd == NULL || pPreOrder ==NULL)
        {
            return;
        }
        tempLen++;
        //in case that overflow
        if(tempLen > treeLen)
        {
            return;
        }
        leftEnd++;
    }
    int nLeftLen = tempLen;
    int nRightLen = treeLen - 1 - tempLen;
    if(nLeftLen>=1)
    {
        rebuild(pPreOrder+1, pInOrder, nLeftLen, &((*pRoot)->pLeft));
    }
    if(nRightLen>=1)
    {
        rebuild(pPreOrder+nLeftLen+1, leftEnd+1, nRightLen, &((*pRoot)->pRight));
    }
}

void preOrderTreval(NODE *pRoot)
{
    if(pRoot==NULL)
    {
        return;
    }
    cout<<pRoot->chVal<<" ";
    preOrderTreval(pRoot->pLeft);
    preOrderTreval(pRoot->pRight);
}
int main()
{
    char szPreOrder[TREELEN] = {'a', 'b', 'd', 'c', 'e', 'f'};
    char szInOrder[TREELEN] = {'d', 'b', 'a', 'e', 'c', 'f'};

    NODE *pRoot = NULL;
    rebuild(szPreOrder, szInOrder, TREELEN, &pRoot);
    preOrderTreval(pRoot);
    return 0;
}