Minimum Depth of Binary Tree

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题目地址：https://leetcode.com/problems/minimum-depth-of-binary-tree/

Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

这个题目正好与求树高的方法相反，求根节点到叶子节点最短路径的长度，依然用递归实现，注意左右子树只有存在其一时候的情况的处理：

public class MinimumDepthOfBinaryTree {    public static int minDepth(TreeNode root) {        if (root == null)            return 0;        else if (root.left == null && root.right == null)            return 1;        else if (root.left != null && root.right == null)            return minDepth(root.left) + 1;        else if (root.left == null && root.right != null)            return minDepth(root.right) + 1;        else            return Math.min(minDepth(root.left) + 1, minDepth(root.right) + 1);    }    public static void main(String[] args) {        TreeNode node1 = new TreeNode(5);        TreeNode node2 = new TreeNode(4);        TreeNode node3 = new TreeNode(8);        TreeNode node4 = new TreeNode(11);        TreeNode node5 = new TreeNode(13);        TreeNode node6 = new TreeNode(4);        TreeNode node7 = new TreeNode(7);        TreeNode node8 = new TreeNode(2);        TreeNode node9 = new TreeNode(1);        node1.left = node2;        node1.right =node3;        node2.left = node4;        node3.left = node5;        node3.right = node6;        node4.left = node7;        node4.right = node8;        node6.right = node9;        System.out.println(minDepth(node1));    }}

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