leetcode — maximum-depth-of-binary-tree

/**
 *
 * Source : https://oj.leetcode.com/problems/maximum-depth-of-binary-tree/
 *
 *
 *
 * Given a binary tree, find its maximum depth.
 *
 * The maximum depth is the number of nodes along the longest path from the root node
 * down to the farthest leaf node.
 */
public class MaxDepthOfBinaryTree {

    /**
     * 求出二叉树树的深度，使用深度优先
     *
     * @param root
     * @return
     */
    public int maxDepth (TreeNode root) {
        if (root == null) {
            return 0;
        }
        int leftMax = 1;
        int rightMax = 1;
        leftMax += maxDepth(root.leftChild);
        rightMax += maxDepth(root.rightChild);

        return Math.max(leftMax, rightMax);
    }

    public TreeNode createTree (char[] treeArr) {
        TreeNode[] tree = new TreeNode[treeArr.length];
        for (int i = 0; i < treeArr.length; i++) {
            if (treeArr[i] == '#') {
                tree[i] = null;
                continue;
            }
            tree[i] = new TreeNode(treeArr[i]-'0');
        }
        int pos = 0;
        for (int i = 0; i < treeArr.length && pos < treeArr.length-1; i++) {
            if (tree[i] != null) {
                tree[i].leftChild = tree[++pos];
                if (pos < treeArr.length-1) {
                    tree[i].rightChild = tree[++pos];
                }
            }
        }
        return tree[0];
    }

    private class TreeNode {
        TreeNode leftChild;
        TreeNode rightChild;
        int value;

        public TreeNode(int value) {
            this.value = value;
        }

        public TreeNode() {

        }
    }

    public static void main(String[] args) {
        MaxDepthOfBinaryTree depthOfBinaryTree = new MaxDepthOfBinaryTree();
        char[] arr = new char[]{'3','9','2','#','#','1','7'};

        System.out.println(depthOfBinaryTree.maxDepth(depthOfBinaryTree.createTree(arr)));
    }
}