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[leetcode] problem 543 – diameter of binary tree

admin 11月 13, 2020 0

Given a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.

Example

Given a binary tree

Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3].

Note

The length of path between two nodes is represented by the number of edges between them.

Code

public class  {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) { val = x; }
}

private int max = 1;

public int diameterOfBinaryTree(TreeNode root) {
    dfs(root);
    return max - 1;
}

private int dfs(TreeNode root) {
    if (root == null)
        return 0;

    int left = dfs(root.left);
    int right = dfs(root.right);

    max = Math.max(max, left + right + 1);

    return Math.max(left, right) + 1;
}