leetcode Convert Sorted Array to Binary Search Tree
利用更有序数组,构造平衡二叉树。
思路,递归,每次中间节点为根节点,然后递归获得左右子树。
/** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: TreeNode *fun(vector<int> &num, int start, int end) { if (start > end) return NULL; int mid = (start + end) / 2; TreeNode *root = new TreeNode(num[mid]); root -> left = fun(num, start, mid - 1); root -> right = fun(num, mid + 1, end); return root; } TreeNode *sortedArrayToBST(vector<int> &num) { return fun(num, 0, num.size() - 1); } };