leetCode打卡——108 Convert Sorted Array to Binary Search Tree

题目

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

思路

将传入的数组，取中间的数作为当前节点的值，两侧的子数组构成子树
两侧的子数组按照步骤1进行，直到只剩下一个值，那么就结束递归

var sortedArrayToBST = function(nums) {
    return run(nums);
};

var run = function(nums) {
    if (nums.length === 0) return null;

    const midIndex = Math.floor(nums.length  / 2);

    const nowNode = new TreeNode(nums[midIndex]);

    const leftNums = nums.slice(0, midIndex);
    const rightNums = nums.slice(midIndex + 1);

    nowNode.left = run(leftNums);

    nowNode.right = run(rightNums);
    

    return nowNode;
}