111. 二叉树的最小深度

111. 二叉树的最小深度

https://leetcode-cn.com/problems/minimum-depth-of-binary-tree/description/

package com.test;

import java.util.ArrayList;
import java.util.List;

/**
 * @Author stono
 * @Date 2018/9/3 上午8:06
 */
public class Lesson111 {
    public static void main(String[] args) {
        TreeNode t1 = new TreeNode(1);
        TreeNode t2L = new TreeNode(2);
        TreeNode t2R = new TreeNode(2);
        TreeNode t3_1 = new TreeNode(3);
        TreeNode t3_2 = new TreeNode(4);
        TreeNode t3_3 = new TreeNode(4);
        TreeNode t3_4 = new TreeNode(3);
        t1.left = t2L;
        t1.right = t2R;
        t2L.left = t3_1;
        t2L.right = t3_2;
        t2R.left = t3_3;
        t2R.right = t3_4;

        int i = minDepth(t1);
        System.out.println(i);

    }

    public static int minDepth(TreeNode root) {
        if (root == null) {
            return 0;
        }
        List<Integer> list = new ArrayList<>(8);
        minDepth(1, root, list);
        int min = list.get(0);
        for (int i = 1; i < list.size(); i++) {
            if (list.get(i) < min) {
                min = list.get(i);
            }
        }
        return min;
    }

    /**
     * 把中间的结果都进行缓存
     * @param i
     * @param root
     * @param list
     */
    private static void minDepth(int i, TreeNode root, List<Integer> list) {
        // 叶子节点的情况
        if (root.left == null && root.right == null) {
            list.add(i);
        } else {
            if (root.left != null) {
                minDepth(i + 1, root.left, list);
            }
            if (root.right != null) {
                minDepth(i + 1, root.right, list);
            }
        }
    }
}