-
Notifications
You must be signed in to change notification settings - Fork 7
/
Main.java
54 lines (47 loc) · 1.64 KB
/
Main.java
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
package com.company;
import java.util.Arrays;
class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode() {}
TreeNode(int val) { this.val = val; }
TreeNode(int val, TreeNode left, TreeNode right) {
this.val = val;
this.left = left;
this.right = right;
}
}
public class Main {
public static void main(String[] args) {
int[] preorder = {3, 9, 20, 15, 7};
int[] inorder = {9, 3, 15, 20, 7};
buildTree(preorder, inorder);
}
public static TreeNode buildTree(int[] preorder, int[] inorder) {
if(preorder.length == 0 || inorder.length == 0) return null;
TreeNode root = new TreeNode(preorder[0]);
int index = indexOf(inorder, preorder[0]);
int[] leftInorder = copyArray(inorder, 0, index - 1);
int[] leftPreorder = copyArray(preorder, 1, leftInorder.length);
int[] rightPreorder = copyArray(preorder, leftInorder.length + 1, preorder.length - 1);
int[] rightInorder = copyArray(inorder, index + 1, inorder.length - 1);
root.left = buildTree(leftPreorder, leftInorder);
root.right = buildTree(rightPreorder, rightInorder);
return root;
}
private static int[] copyArray(int[] arr, int left, int right){
int[] res = new int[right - left + 1];
int index = 0;
for (int i = left; i <= right; i++)
res[index++] = arr[i];
return res;
}
private static int indexOf(int[] arr, int target){
for (int i = 0; i < arr.length; i++) {
if(arr[i] == target)
return i;
}
return -1;
}
}