1382. balancing binary search tree - General method

1382. Balance the binary search tree

Here's a binary search tree , Please return to a tree After balancing Binary search tree of , The newly generated tree should have the same node value as the original tree . If there are multiple construction methods , Please return to any one .

If a binary search tree , The height difference between the two subtrees of each node shall not exceed 1 , We call this binary search tree The balance of .

Example 1：

Input ：root = [1,null,2,null,3,null,4,null,null]
Output ：[2,1,3,null,null,null,4]
explain ： This is not the only correct answer ,[3,1,4,null,2,null,null] It is also a feasible construction scheme .

Example 2：

Input : root = [2,1,3]
Output : [2,1,3]

The solution code is as follows ：

/** * Definition for a binary tree node. * struct TreeNode { * int val; * struct TreeNode *left; * struct TreeNode *right; * }; */
 int len;
 void or_search(struct TreeNode* root){
    
     if(root){
    
          or_search(root->left);
           len++;

         or_search(root->right);
          
    
     }
    
 }
 void or_search2(struct TreeNode* root,int *a){
    
     if(root){
    
          or_search2(root->left,a);
          a[len++]=root->val;

         or_search2(root->right,a);
     }
 }
  void creat_root(struct TreeNode** root,int *a,int low,int high){
    
      if(low<=high){
    
      int mid=(low+high)/2;
      (*root)->val=a[mid];
      (*root)->left=(struct TreeNode*)malloc(sizeof(struct TreeNode));
       (*root)->right=(struct TreeNode*)malloc(sizeof(struct TreeNode));
       creat_root(&((*root)->left),a,low,mid-1);
       creat_root(&((*root)->right),a,mid+1,high);
        }
        else{
    
            (*root)=NULL;
        }


  }


struct TreeNode* balanceBST(struct TreeNode* root){
    
    len=0;
    or_search(root);
   struct TreeNode* re=(struct TreeNode*)malloc(sizeof(struct TreeNode));
    int *a=(int *)malloc(sizeof(int)*len);
    len=0;
     or_search2(root,a);
     printf("len %d ",len);
     creat_root(&re,a,0,len-1);
     return re;


}