小编The*_*e87的帖子

在Java的类TreeSet文档中,其中一个构造函数显示为具有以下标题:

TreeSet(Comparator<? super E> c)

有人可以帮助解释为什么TreeSet的构造函数将比较器对象作为其参数吗？我不知道为什么要这样做.

我查看了其他各种StackOverflow答案,它们都与我的讲师在幻灯片中写的不同.

深度优先搜索的时间复杂度为O(b ^ m),其中b是搜索树的最大分支因子,m是状态空间的最大深度.如果m比d大得多,但是如果搜索树是"浓密的",则可能比广度优先搜索快得多.

他继续说..

空间复杂度为O(bm),即动作序列长度的空间线性!只需存储从根节点到叶节点的单个路径,以及路径上每个节点的剩余未扩展兄弟节点.

StackOverflow的另一个答案表明它是O(n + m).

我的书中有一个问题说(没有答案):

假设我们有一个使用标头声明的类Beta:

class Beta extends Alpha

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所以Beta是Alpha的子类,而在Alpha类中有一个带头的方法:

public int value(Gamma gam) throws ValueException

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编写一个名为addValues静态方法,该方法采用了一个对象,其可以是式的ArrayList<Alpha>或ArrayList<Beta>,并且还类型的对象Gamma.对方法addValues的调用必须返回通过在ArrayList参数中的每个对象上添加值调用的结果而获得的总和,其中Gamma参数作为每次值调用的参数.在计算总和时,应忽略任何导致抛出ValueException类型异常的值调用.

我的尝试:

public static int addValues(ArrayList<? extends Alpha> arr, Gamma gam) {
    int sum = 0;
    for (int i = 0; i < arr.size(); i++) {
        try {
            sum += arr.get(i) + gam;
        } catch (Exception e) {
            i++;
        }
    }
    return sum;
}

虽然我知道对于初学者来说这条线sum += arr.get(i) + gam会给我一个错误,因为它们不是直接int的,可以添加.这本书没有提供关于这个问题的更多信息,所以我在这里写的是问题所需的一切.

我的代码出现了这个错误,我一步一步地按照谷歌教程说明进行操作.

Pick Place error: The operation couldn’t be completed. The Places API could not find the user's location. This may be because the user has not allowed the application to access location information.

我已将相关信息添加到info.plist中,我的代码如下所示 -

import UIKit
import GooglePlaces

class ViewController: UIViewController {

    var placesClient: GMSPlacesClient!

    @IBOutlet var nameLabel: UILabel!
    @IBOutlet var addressLabel: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
        let locationManager = CLLocationManager()
        locationManager.requestWhenInUseAuthorization()
        locationManager.startUpdatingLocation()
        placesClient = GMSPlacesClient.shared()
    }

    @IBAction func getCurrentPlace(_ sender: UIButton) {


        placesClient.currentPlace(callback: { (placeLikelihoodList, error) -> …

TypeError at /api/team/
The `fields` option must be a list or tuple or "__all__". Got str.
Request Method: GET
Request URL:    http://127.0.0.1:8000/api/team/
Django Version: 1.9
Exception Type: TypeError
Exception Value:    
The `fields` option must be a list or tuple or "__all__". Got str.
Exception Location: /Library/Python/2.7/site-packages/rest_framework/serializers.py in get_field_names, line 971
Python Executable:  /usr/bin/python
Python Version: 2.7.10
Python Path:    
['/Desktop/webprog/python/wsgi/openshift',
 '/Library/Python/2.7/site-packages/Django-1.9-py2.7.egg',
 '/Library/Python/2.7/site-packages',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python27.zip',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-darwin',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-mac',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-mac/lib-scriptpackages',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-old',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload',
 '/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/PyObjC']
Server time:    Mon, 28 Mar 2016 14:42:11 +0000

这个错误意味着什么,它发生在哪里？它说Exception …

我正在尝试使用 set_password() 函数，但出现此错误

'Member' object has no attribute 'set_password'

当我使用它时出现。如果我取出 set_password() 函数，密码将存储在数据库中，但不会被散列。

查看.py

user = Member(username=u, password=p, email=e, security=s)
user.set_password(p)
user.save()

模型.py

class Member(models.Model):
    username = models.CharField(max_length=16,primary_key=True)
    password = models.CharField(max_length=16)
    email = models.CharField(max_length=325)
    security = models.CharField(max_length=16)
    profile = models.OneToOneField(Profile, null=True)
    following = models.ManyToManyField("self", symmetrical=False)
    from_member_id = models.CharField(max_length=16)

    def __str__(self):
        return self.username