java算法-树的子结构

/**
 * @author bingo
 * @since 2018/11/22
 */

/*
 public class TreeNode {
 int val = 0;
 TreeNode left = null;
 TreeNode right = null;

 public TreeNode(int val) {
 this.val = val;

 }

 }
 */
public class Solution {
    /**
     * 判断root2是否是root1的子树
     * @param root1 树1
     * @param root2 树2
     * @return 是否是子树
     */
    public boolean HasSubtree(TreeNode root1, TreeNode root2) {
        boolean res = false;
        if (root1 != null && root2 != null) {
            if (root1.val == root2.val) {
                res = isSame(root1, root2);
            }
            if (!res) {
                res = HasSubtree(root1.left, root2);
            }
            if (!res) {
                res = HasSubtree(root1.right, root2);
            }
        }

        return res;
    }

    private boolean isSame(TreeNode root1, TreeNode root2) {
        if (root2 == null) {
            return true;
        }
        if (root1 == null) {
            return false;
        }
        if (root1.val != root2.val) {
            return false;
        }
        return isSame(root1.left, root2.left) && isSame(root1.right, root2.right);
    }
}