[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.

 

Idea: Recursive Implementation, with a smaller depth of + 1 in the left and right nodes.

NOTE: If either of the left and right subtree is null, the depth of the subtree that is not null should prevail, rather than the depth 0 of null.

 

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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