[LeetCode] Convert Sorted Array to Binary Search Tree

原创于 2014-12-25 13:42:40 发布 · 250 阅读

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本文介绍了一种将已排序的数组转换为高度平衡的二叉搜索树的方法。通过递归地选择中间元素作为根节点，并将左半部分和右半部分的数组分别作为左右子树来构造整个树结构。

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

/**
 * 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 *generate(vector<int> &num,int left,int right){
        if(left > right) return NULL;
        int mid = (left + right) / 2;
        TreeNode *tleft = generate(num,left,mid - 1);
        TreeNode *tright = generate(num,mid + 1,right);
        TreeNode *root = new TreeNode(num[mid]);
        root -> left = tleft;
        root -> right = tright;
        return root;
    }
     TreeNode *sortedArrayToBST(vector<int> &num) {
        int len = num.size();
        return generate(num,0,len - 1);
    }
};