二叉树的最小深度

/**
 * Given a binary tree, find its minimum depth using Java Streams.
 * The approach is similar to the non-stream approach but leverages streams for clarity and conciseness.
 * 
 * Approach:
 * 1. If the root is null, return 0.
 * 2. If the root has no left child, return the minimum depth of the right subtree plus one.
 * 3. If the root has no right child, return the minimum depth of the left subtree plus one.
 * 4. Use streams to determine the minimum depth of the left and right subtrees.
 */
import java.util.stream.Stream;
 
public class Solution {
    public int minDepth(TreeNode root) {
        if (root == null) return 0;
        return Stream.of(root.left, root.right)
                     .mapToInt(child -> child == null ? Integer.MAX_VALUE : minDepth(child))
                     .min().getAsInt() + 1;
    }
}