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Leetcode:Convert Sorted Array to Binary Search Tree

Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

分析:对于BST,左右子树的高度差小于等于1,则在由sorted array构建BST时把数组中间元素作为根节点,然后递归的构建左右子树。代码如下:

 1 class Solution { 2 public: 3     TreeNode *sortedArrayToBST(vector<int> &num) { 4         return build_BST(num, 0, num.size()-1); 5     } 6      7     TreeNode *build_BST(vector<int> &num, int start, int end){ 8         if(start > end) return NULL; 9         10         int mid = (start + end)/2;11         TreeNode *root = new TreeNode(num[mid]);12         root->left = build_BST(num, start, mid-1);13         root->right = build_BST(num, mid+1, end);14         15         return root;16     }17 };

 

Leetcode:Convert Sorted Array to Binary Search Tree