Maximum Sum BST in Binary Tree LeetCode solution in Java

1
class Solution {
2

3
  int ans = 0;
4

5
  public int maxSumBST(TreeNode root) {
6
    solve(root);
7
    return ans;
8
  }
9

10
  // int[] = { min, max, sum };
11
  private int[] solve(TreeNode root) {
12
    if (root == null) return new int[] {Integer.MAX_VALUE, Integer.MIN_VALUE, 0};
13

14
    int[] left = solve(root.left);
15
    int[] right = solve(root.right);
16

17
    if (root.val > left[1] && root.val < right[0]) {
18
      int sum = left[2] + right[2] + root.val;
19
      ans = Math.max(ans, sum);
20
      return new int[] {Math.min(left[0], root.val), Math.max(root.val, right[1]), sum};
21
    }
22

23
    return new int[] {Integer.MIN_VALUE, Integer.MAX_VALUE, 0};
24
  }
25
}