這題要把陣列轉成一個二元樹。
LeetCode 題目連結
https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/
題目
Given an array where elements are sorted in ascending order, convert it to a height balanced BST.
For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
Example:
Given the sorted array: [-10,-3,0,5,9],
One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST:
0
/ \
-3 9
/ /
-10 5
Accept 作法
利用遞迴的方式不斷的把陣列分兩半，因為陣列已經排序好，再分配左子樹和右子樹。Runtime: 0 ms
Memory: 39.4 MB
Java 程式碼
class Solution {
public TreeNode sortedArrayToBST(int[] nums) {
return BST(nums,0,nums.length - 1);
}
TreeNode BST(int[] nums,int start,int end){
if(start > end){
return null;
}
int halfSize = (start+ end) /2;
TreeNode node = new TreeNode();
node.val = nums[halfSize];
node.left = BST(nums,start,halfSize - 1);
node.right = BST(nums,halfSize+1,end);
return node;
}
}
更多 LeetCode 相關資源
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除了 LeetCode 練習外，我也入手了這本，題庫來自真正的面試，並非摘自教科書。它們反映出頂尖公司真正會出的題目，你可以藉此做好充分準備。
需要的話可以看看，寫得很仔細。
需要的話可以看看，寫得很仔細。
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