二叉树的重建

#include <iostream> using namespace std; const char preOrder[] = "abdcef"; const char inOrder[] = "dbaecf"; const int size = sizeof preOrder / sizeof *preOrder; struct Node { char data; Node *left; Node *right; }; void Reconstruct(const char *pPre, const char *pIn, int size, Node **pRoot) { if(pPre == NULL || pIn == NULL) return; Node *pTemp = new Node; pTemp->data = *pPre; pTemp->left = NULL; pTemp->right = NULL; if(*pRoot == NULL) *pRoot = pTemp; int pos = 0; const char *ppIn = pIn; while(*ppIn != *pPre) { pos++; ppIn++; } int leftLen = pos; int rightLen = size - pos - 1; if(leftLen > 0) Reconstruct(pPre + 1, pIn, leftLen, &((*pRoot)->left)); if(rightLen > 0) Reconstruct(pPre + leftLen + 1, pIn + leftLen + 1, rightLen, &((*pRoot)->right)); } void InOrder(Node *root) { if(root) { InOrder(root->left); cout << root->data << " "; InOrder(root->right); } } void PreOrder(Node *root) { if(root) { cout << root->data << " "; PreOrder(root->left); PreOrder(root->right); } } void main() { Node *root = NULL; Reconstruct(preOrder, inOrder, size, &root); PreOrder(root); }

上面是编程之美上的解法，下面是自己的解法：

#include <iostream>
#include <queue>

using namespace std;

struct Node 
{
	Node(int i = -1, Node *pLeft = NULL, Node *pRight = NULL) : data(i), left(pLeft), right(pRight) {}
	int data;
	Node *left;
	Node *right;
};

const char *preOrder = "12473568";
const char *inOrder = "47215386";

void printLevel(Node *root)
{
	if (root == NULL)
		return;

	queue<Node *> nqueue;
	nqueue.push(root);

	int start = 0;
	int last = 1;
	int tempLast = last;
	while (!nqueue.empty())
	{
		Node *top = nqueue.front();
		nqueue.pop();
		cout << top->data << " ";

		if (top->left)
		{
			nqueue.push(top->left);
			last++;
		}
		if (top->right)
		{
			nqueue.push(top->right);
			last++;
		}

		start++;
		if (start == tempLast)
		{
			tempLast = last;
			cout << endl;
		}
	}
}

Node *_construct(const char *preOrder, const int preLength,
				 const char *inOrder, const int inLength)
{
	if (preOrder == NULL || preLength <= 0 || inOrder == NULL || inLength <= 0)
		return NULL;

	int pos = inLength;
	for (int i = 0; i < inLength; i++)
	{
		if (inOrder[i] == *preOrder)
		{
			pos = i;
			break;
		}
	}
	if (pos == inLength)
	{
		cout << "wrong" << endl;
		return NULL;
	}
	cout << *preOrder << " ";
	Node *newNode = new Node(*preOrder - '0');
	newNode->left = _construct(preOrder + 1, preLength - 1, inOrder, pos);
	newNode->right = _construct(preOrder + pos + 1, preLength - 1, inOrder + pos + 1, inLength - pos - 1);

	return newNode;
}

Node *construct(const char *preOrder, const char *inOrder)
{
	if (preOrder == NULL || inOrder == NULL)
		return NULL;

	int preLength = strlen(preOrder);
	int inLength = strlen(inOrder);

	return _construct(preOrder, preLength, inOrder, inLength);
}

void preTranverse(Node *root)
{
	if (root == NULL)
		return;
	cout << root->data << " ";
	preTranverse(root->left);
	preTranverse(root->right);
}

void main()
{
	Node *root = construct(preOrder, inOrder);
	cout << endl;

	if (root != NULL)
	{
		preTranverse(root);
	}
	else
	{
		cout << "wrong" << endl;
	}
}