二叉排序树（二叉搜索树）的建立

二叉排序树（二叉搜索树）的建立

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        return BST(nums,0,nums.size()-1);
    }
    TreeNode* BST(vector<int>&nums,int l,int r){
        if(l>r)return NULL;
        int  mid=(r-l)/2+l;
        TreeNode* root=new TreeNode(nums[mid]);
        root->left=BST(nums,l,mid-1);
        root->right=BST(nums,mid+1,r);
        return root;
    }
};