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)));
}
}