树的子结构

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

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

}

}
*/
public class Solution {
public boolean HasSubtree(TreeNode root1,TreeNode root2) {
boolean flag = false;
if(root1 != null && root2 != null){
if(root1.val == root2.val){
flag = isTheSame(root1,root2);
}
if(flag == false){
flag = HasSubtree(root1.left, root2);
}
if(flag == false){
flag = HasSubtree(root1.right, root2);
}
}

return flag;

}

private boolean isTheSame(TreeNode root1, TreeNode root2) {
//表示已经判断了最后一个节点
if(root2 == null)
return true;
if(root1 == null)
return false;
if(root1.val != root2.val) return false;
return isTheSame(root1.left, root2.left) && isTheSame(root1.right, root2.right);
}

}