Minimum Depth of Binary Tree

/** * Definition for binary tree * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public int minDepth(TreeNode root) {        int res = 0;if (root == null) {return res;}if(root.left == null && root.right == null){return 1;}ArrayList<TreeNode> tmp = new ArrayList<TreeNode>();tmp.add(root);boolean finded = false;boolean findedLeft = false;boolean findedRight = false;while(tmp.size() != 0){ArrayList<TreeNode> next = new ArrayList<TreeNode>();for(int i = 0 ; i < tmp.size() ; i++){if(tmp.get(i).left != null){next.add(tmp.get(i).left);findedLeft = false;}else{findedLeft = true;}if(tmp.get(i).right != null){next.add(tmp.get(i).right);findedRight = false;}else{findedRight = true;}if(findedLeft && findedRight){finded = true;break;}}res++;if(finded){break;}tmp = next;}return res < 2 ? 2 : res;    }}

理解了这个概念，改了好多次