leetcode/javascript/0108-convert-sorted-array-to-binary-search-tree.js at main · neetcode-gh/leetcode · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */

/**
 * DFS - Preorder | Left as mid
 * Time O(N) | Space O(log(N))
 * https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/
 * @param {number[]} nums
 * @return {TreeNode}
 */
var sortedArrayToBST = (nums, left = 0, right = nums.length - 1) => {
    const isBaseCase = right < left;
    if (isBaseCase) return null;

    return dfs(nums, left, right); /* Time O(N) | Space O(log(N)) */
};

var dfs = (nums, left, right) => {
    const mid = (left + right) >> 1;

    const root = new TreeNode(
        nums[mid],
    ); /*           | Ignore Auxillary Space O(N) */

    root.left = sortedArrayToBST(
        nums,
        left,
        mid - 1,
    ); /* Time O(N) | Space O(log(N)) */
    root.right = sortedArrayToBST(
        nums,
        mid + 1,
        right,
    ); /* Time O(N) | Space O(log(N)) */

    return root;
};

/**
 * DFS - Preorder | Right as mid
 * Time O(N) | Space O(log(N))
 * https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/
 * @param {number[]} nums
 * @return {TreeNode}
 */
var sortedArrayToBST = (nums, left = 0, right = nums.length - 1) => {
    const isBaseCase = right < left;
    if (isBaseCase) return null;

    return dfs(nums, left, right); /* Time O(N) | Space O(log(N)) */
};

var dfs = (nums, left, right) => {
    let mid = (left + right) >> 1;

    const isOdd = (left + right) % 2 === 1;
    if (isOdd) mid += 1;

    const root = new TreeNode(
        nums[mid],
    ); /*           | Ignore Auxillary Space O(N) */

    root.left = sortedArrayToBST(
        nums,
        left,
        mid - 1,
    ); /* Time O(N) | Space O(log(N)) */
    root.right = sortedArrayToBST(
        nums,
        mid + 1,
        right,
    ); /* Time O(N) | Space O(log(N)) */

    return root;
};

/**
 * DFS - Preorder | Random as mid
 * Time O(N) | Space O(log(N))
 * https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/
 * @param {number[]} nums
 * @return {TreeNode}
 */
var sortedArrayToBST = (nums, left = 0, right = nums.length - 1) => {
    const isBaseCase = right < left;
    if (isBaseCase) return null;

    return dfs(nums, left, right); /* Time O(N) | Space O(log(N)) */
};

var dfs = (nums, left, right) => {
    let mid = (left + right) >> 1;

    const isOdd = (left + right) % 2 === 1;
    if (isOdd) mid += Math.floor(Math.random() * 2);

    const root = new TreeNode(
        nums[mid],
    ); /*           | Ignore Auxillary Space O(N) */

    root.left = sortedArrayToBST(
        nums,
        left,
        mid - 1,
    ); /* Time O(N) | Space O(log(N)) */
    root.right = sortedArrayToBST(
        nums,
        mid + 1,
        right,
    ); /* Time O(N) | Space O(log(N)) */

    return root;
};