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[leetcode] 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.

 

思路:递归实现,取左右节点中深度小的+1。

  注意:如果左右子树其中一个为null,则应以不为null的子树深度为准,而不是以null的深度0为准。

 

public class Solution {    public int minDepth(TreeNode root) {        if (root == null)            return 0;        if (root.left == null)            return minDepth(root.right) + 1;        if (root.right == null)            return minDepth(root.left) + 1;        else        {            int minLeft = minDepth(root.left);            int minRight = minDepth(root.right);            return (minLeft < minRight ? minLeft : minRight) + 1;        }    }    public static void main(String[] args) {        TreeNode root = new TreeNode(10);        root.left = new TreeNode(5);        root.right = new TreeNode(5);        root.right.left = new TreeNode(9);        System.out.println(new Solution().minDepth(root));    }}
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