剑指Offer 通过中序和先序遍历重建二叉树

 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<int> pre,vector<int> in) {
13 
14         m_pre=pre;
15         m_in=in;
16         TreeNode* head;
17         head=reConstruct(0,pre.size()-1,0,in.size()-1);
18         return head;
19     }
20     
21     struct TreeNode* reConstruct(int pre_L,int pre_R,int in_L,int in_R)
22     {
23         if(pre_L>pre_R||in_L>in_R)
24             return nullptr;
25 
26         TreeNode *root = new TreeNode(m_pre[pre_L]);
27         int i=0;
28         while(m_pre[pre_L]!=m_in[i])
29             i++;
30         
31         root->left=reConstruct(pre_L+1,pre_L+i-in_L,in_L,i-1);
32         root->right=reConstruct(i+pre_L+1-in_L,pre_R,i+1,in_R);
33         
34         return root;
35     }
36     
37 private:
38        //代替全局变量
39     vector<int> m_pre;
40     vector<int> m_in;
41 
42 };