[Leetcode][BST][Convert Sorted Array to Binary Search Tree]
把一个排好序的vector转换为一颗二分查找树。
很简单的题目,递归即可,保证边界不要出错。
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 typedef vector<int>::iterator Iter; 13 TreeNode *toBST(Iter begin, Iter end) { 14 int n = end - begin; 15 if (n <= 0) { 16 return NULL; 17 } 18 int pos = n / 2; 19 TreeNode *node = new TreeNode(*(begin + pos)); 20 node->left = toBST(begin, begin + pos); 21 node->right = toBST(begin + pos + 1, end); 22 return node; 23 } 24 TreeNode *sortedArrayToBST(vector<int> &num) { 25 return toBST(num.begin(), num.end()); 26 } 27 };
一次AC。