LeetCode - Minimum Depth of Binary Tree

題目：

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：

遞歸，註意是到leaf node，所以有一個孩子為空的話，則取非空的那一孩子

package tree;

public class MinimumDepthOfBinaryTree {
    
    public int minDepth(TreeNode root) {
        if (root == null) return 0;
        if (root.left == null || root.right == null) return root.left == null ? (1 + minDepth(root.right)) : (1 + minDepth(root.left));
        return Math.min(1 + minDepth(root.left), 1 + minDepth(root.right));
    }
    
}