剑指offer NO4 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,

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* reConstructBinaryTree(vector<int> pre,vector<int> in) {
           int len=in.size();
        if(len==0)return NULL;
        vector<int>left_pre,right_pre;
        vector<int>left_in,right_in;
       TreeNode* head=new TreeNode(pre[0]);
        int index=0;
        for(int i=0;i<len;i++)
        {
            if(in[i]==pre[0])
            {
                index=i;
                break;
                
            }
        }
        for(int i=0;i<index;i++)
        {
            left_pre.push_back(pre[i+1]);
            left_in.push_back(in[i]);
            
        }
        for(int i=index+1;i<len;i++)
        {
            right_pre.push_back(pre[i]);
            right_in.push_back(in[i]);
        }
        head->left=reConstructBinaryTree(left_pre,left_in);
        head->right=reConstructBinaryTree(right_pre,right_in);
        
        return head;

            
     

    }
};