子树判断

private static boolean hasSubTree(TreeNode A,TreeNode B){
boolean result=false;
if(A!=null&&B!=null){
if(A.val==B.val){
result=isSubTree(A,B);
}
if(!result){
hasSubTree(A.left, B);
}
if(!result){
hasSubTree(A.right, B);
}
}
return result;
}

private static boolean isSubTree(TreeNode a, TreeNode b) {
if(a==null)
return false;
if(b==null)
return true;
if(a.val!=b.val)
return false;
return isSubTree(a.left, b.left)&&isSubTree(a.right, b.right);
}