树的子结构（java递归实现）

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean hasSubtree(TreeNode pRoot1, TreeNode pRoot2) {
       if (pRoot1 == null || pRoot2 == null)
            return false;
        if (isPart(pRoot1, pRoot2))
            return true;
        return hasSubtree(pRoot1.left, pRoot2) || hasSubtree(pRoot1.right, pRoot2);
    }

    private boolean isPart(TreeNode pRoot1, TreeNode pRoot2) {
        if (pRoot2 == null)
            return true;
        if (pRoot1 == null || pRoot1.val != pRoot2.val)
            return false;
        return isPart(pRoot1.left, pRoot2.left) && isPart(pRoot1.right, pRoot2.right);
    }
}