重建二叉树

题目描述

输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回。

root->left=reConstructBinaryTree(preleft,inleft);
root->right=reConstructBinaryTree(preright,inright);
return root;
}
};/**
* Definition for binary tree
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
struct TreeNode* reConstructBinaryTree(vector<int> pre,vector<int> in) {
if (pre.empty() || in.empty() || pre.size()!=in.size()){
return NULL;
}
TreeNode* root=new TreeNode(pre[0]);
int len=in.size();
int i,k=-1;
vector<int>  preleft,preright,inleft,inright;
for(i=0;i<len;i++)
{
if(pre[0]==in[i])
{
k=i;
break;
}
}
if(k==-1)
return NULL;

for(i=0;i<len;i++)
{
if(i<k)
inleft.push_back(in[i]);
if(i>k)
inright.push_back(in[i]);
}
k=inleft.size()+1;
for(i=1;i<pre.size();i++)
if(i<k)
preleft.push_back(pre[i]);
else
preright.push_back(pre[i]);