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。

 

1 /** 2  * Definition for binary tree 3  * struct TreeNode { 4  *     int val; 5  *     TreeNode *left; 6  *     TreeNode *right; 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8  * }; 9  */10 class Solution {11 public:12     struct TreeNode* reConstructBinaryTree(vector
      
        pre,vector
       
         in) {13         if (pre.size() != 0 && in.size() != 0 && pre.size() == in.size())14             {15                 return build(pre,in,0,pre.size()-1,0,in.size()-1);16             }17         else18             {19                 return NULL;20             }21         22     }23     24     struct TreeNode* build(vector
        
          pre,vector
         
           in,int l1,int r1,int l2,int r2)25     {26     if(l1<=r1)27     {28         int i=l2;29         while(pre[l1]!=in[i])30             i++;31         TreeNode* T= new TreeNode(in[i]);32         T->left=build(pre,in,l1+1,l1+i-l2,l2,i-1);33         T->right=build(pre,in,l1+i-l2+1,r1,i+1,r2);34         return T;35     }36     else return NULL;37     }38 };