108. Convert Sorted Array to Binary Search Tree

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */

static int wing=[]()
{
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();

class Solution 
{
public:
    TreeNode* sortedArrayToBST(vector<int>& nums) 
    {
        if(nums.size()==0)
            return NULL;
        if(nums.size()==1)
            return new TreeNode(nums[0]);
        
        int mid=nums.size()/2;
        TreeNode* root=new TreeNode(nums[mid]);
        
        vector<int> vleft(nums.begin(),nums.begin()+mid);
        vector<int> vright(nums.begin()+mid+1,nums.end());
        
        root->left=sortedArrayToBST(vleft);
        root->right=sortedArrayToBST(vright);
        
        return root;
    }
};

递归建树，问题不大