题解 | #二叉树的最小深度#

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {

    private int res = Integer.MAX_VALUE;

    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @return int整型
     */
    public int run (TreeNode root) {
        // write code here
        if (root == null) {
            return 0;
        }
        dfs(root, 0);
        return res;
    }

    private void dfs(TreeNode root, int sum) {
        if (root == null) {
            return;
        }
        sum++;
        if (root.left == null && root.right == null) {
            res = Math.min(res, sum);
        }
        dfs(root.left, sum);
        dfs(root.right, sum);
        sum--;
    }
}