Given a binary tree where each path going from the root to any leaf form a valid sequence, check if a given string is a valid sequence in such binary tree.
We get the given string from the concatenation of an array of integers arr and the concatenation of all values of the nodes along a path results in a sequence in the given binary tree.
Example 1:
Input: root = [0,1,0,0,1,0,null,null,1,0,0], arr = [0,1,0,1]
Output: true
Explanation:
The path 0 -> 1 -> 0 -> 1 is a valid sequence (green color in the figure).
Other valid sequences are:
0 -> 1 -> 1 -> 0
0 -> 0 -> 0
Example 2:
Input: root = [0,1,0,0,1,0,null,null,1,0,0], arr = [0,0,1]
Output: false
Explanation: The path 0 -> 0 -> 1 does not exist, therefore it is not even a sequence.
Example 3:
Input: root = [0,1,0,0,1,0,null,null,1,0,0], arr = [0,1,1] Output: false Explanation: The path 0 -> 1 -> 1 is a sequence, but it is not a valid sequence.
Constraints:
1 <= arr.length <= 5000
0 <= arr[i] <= 9
Each node's value is between [0 - 9].
Solution:
/**
* Definition for a binary tree node.
* public 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;
* }
* }
root = [0,1,0,0,1,0,null,null,1,0,0], arr = [0,1,1]
[0,1,0,0,1,0,null,null,1,0,0]
[0,1,0,1]
0
/ \
1 0
/ \ / \
0 1 0 null
/ \ /\
null,1 0,0
[2,9,3,null,1,null,2,null,8]
[2,9,1,8,0]
2
/ \
9 3
\ \
1 2
\
8
*/
class Solution {
public boolean isValidSequence(TreeNode root, int[] arr) {
if (root == null) {
return false;
}
return isValidSequence(root, arr, 0);
}
public boolean isValidSequence(TreeNode node, int[] arr, int index) {
if (node == null) {
return false;
}
System.out.printf("index %d, node %d\n", index, node.val);
if (index > arr.length - 1) {
return false;
}
if (node.val != arr[index]) {
return false;
}
if (node.left == null && node.right == null && index == arr.length - 1) {
return true;
}
return isValidSequence(node.left, arr, index + 1) ||
isValidSequence(node.right, arr, index + 1);
}
}