111. Minimum Depth of Binary Tree

1 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.

2代碼

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int minDepth(TreeNode root) {
		if (root == null) {
			return 0;
		}
		return treeDeep(root);
	}

	public int treeDeep(TreeNode root) {
		if (root == null) {
			return 0;
		}

		if (root.left == null) {
			return 1 + treeDeep(root.right);
		}
		if (root.right == null) {
			return 1 + treeDeep(root.left);
		}
		int b = 1 + treeDeep(root.right);
		int a = 1 + treeDeep(root.left);
		return Math.min(a, b);
	}
}