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leetcode 00. 相同的树 C语言

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给定两个二叉树，编写一个函数来检验它们是否相同。如果两个树在结构上相同，并且节点具有相同的值，则认为它们是相同的。示例 1: 输入: 1 1 / \ / \ 2 3 2 3 [1,2,3], [1,2,3] 输出: true 示例 2: 输入: 1 1 / \ 2 2 [1,2], [1,null,2] 输出: false 示例 3: 输入: 1 1 / \ / \ 2 1 1 2 [1,2,1], [1,1,2] 输出: false /** * Definition for a binary tree node. * struct TreeNode { * int val; * struct TreeNode *left; * struct TreeNode *right; * }; */ bool isSameTree(struct TreeNode* p, struct TreeNode* q){ if ((p == NULL) && (q == NULL)) { return true; } else if ((p == NULL) || (q == NULL)) { return false; } else if (p->val != q->val) { return false; } return (isSameTree(p->left, q->left)) &&

MPMediaItemArtwork is null while cover is available in iTunes

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问题 The UIImage "image" is always empty ("null") though the cover is shown in the music app by apple. in iOS 7 it works fine, but with iOS 8 I get no cover. Whats wrong with my code, or what has changed in iOS 8? -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { AlbumCell *cell = [tableView dequeueReusableCellWithIdentifier:@"AlbumCell"]; MPMediaItemCollection *song = self.songsList[indexPath.row]; cell.albumName.text = [[song

duplicate null value violation on UNIQUE KEY constraint in Mssql

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问题 MS SQL Server does not ignore the null value and considers it as violation for the UNIQUE KEY constraint but what I know is that the UNIQUE KEY differ from the primary key where it accepts the null value. Violation of UNIQUE KEY constraint 'AK_UserName'. Cannot insert duplicate key in object 'dbo.users'. The duplicate key value is (<NULL>). The statement has been terminated. Can anyone help me to solve this problem? 回答1: you can create a unique index that ignores null values like this CREATE

How to convert the null values to empty string in php array?

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问题 I want to convert this array that Array[4] should not give null it can give blank space (empty string). Array ( [0] => 1 [1] => 4 [2] => 0 [3] => V [4] => [5] => N ); (The reason for the change, unrelated to the general question) Fatal error: Uncaught exception 'PDOException' with message 'Database error [23000]: Column 'message' cannot be null, driver error code is 1048' in 回答1: Then you should just loop through array elements, check each value for null and replace it with empty string.

Where to check if an object is null or not?

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问题 Where do you check if an object that you are passing to a method is null or not? Should an object need to be tested before calling a method? or within the method that is using the argument? public class Program { public static void Main(string[] args) { // Check if person is null here? or within PrintAge? PrintAge(new Person { Age = 1 }); } private static void PrintAge(Person person) { // check if person is null here? Console.WriteLine("Age = {0}", person.Age); } } public class Person {

How to replace all Null values of a dataframe in Pyspark

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问题 I have a data frame in pyspark with more than 300 columns. In these columns there are some columns with values null. For example: Column_1 column_2 null null null null 234 null 125 124 365 187 and so on When I want to do a sum of column_1 I am getting a Null as a result, instead of 724. Now I want to replace the null in all columns of the data frame with empty space. So when I try to do a sum of these columns I don't get a null value but I will get a numerical value. How can we achieve that

How to do unique constraint works with NULL value in MySQL

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问题 I am looking for how to implement unique constraints with NULL check. MySQL shouldn't allow multiple null value. Employee: id | name ---|----- 1 | null 2 | null -> should give error during inserting 2nd row. 回答1: No, MySQL is doing the right thing, according to the SQL-99 specification. https://mariadb.com/kb/en/sql-99/constraint_type-unique-constraint/ A UNIQUE Constraint makes it impossible to COMMIT any operation that would cause the unique key to contain any non-null duplicate values.

Why should someone use {} for initializing an empty object in R?

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问题 It seems that some programmers are using: a = {} a$foo = 1 a$bar = 2 What is the benefit over a = list(foo = 1, bar = 2) ? Why should {} be used? This expression only returns NULL , so a NULL assignment would do the same, wouldn't it? 回答1: Your first query Why should {} be used, this expression only returns NULL , so an NULL assignment would do the same, wouldn't it? Yes, a <- NULL gives the same effect. Using {} is likely to be a personal style. NULL NULL is probably the most versatile and

How to return null from a generic function in Scala?

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问题 I am writing my own simple javax.sql.DataSource implementation, the only method of it I need to work is getConnection: Connection , but the interface inherits many other methods (which I don't need) from javax.sql.CommonDataSource and java.sql.Wrapper . So, I would like to "implement" those unneeded methods a way they wouldn't actually work but would behave an adequate way when called. For example I implement boolean isWrapperFor(Class<?> iface) as def isWrapperFor(iface: Class[_]): Boolean =

Cannot pass null to server using jQuery AJAX. Value received at the server is the string “null”

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问题 I am converting a javascript/php/ajax application to use jQuery to ensure compatibility with browsers other than Firefox. I am having trouble passing true, false, and null values using jQuery's ajax function. Javascript code: $.ajax ( { url : <server_url>, dataType: 'json', type : 'POST', success : receiveAjaxMessage, data: { valueTrue : true, valueFalse: false, valueNull : null } } ); PHP code: var_dump($_POST); Server output: array(3) { ["valueTrue"]=> string(4) "true" ["valueFalse"]=>