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Articles by Anvi Jain
Page 14 of 43
MongoDB Query to search for records only in a specific hour?
For this, use the $hour operator. Let us first create a collection with documents with one of the field as date −> db.mongoDbSearchForHoursDemo.insertOne({"CustomerName":"Larry", "OrderDatetime":new ISODate("2019-01-31 09:45:50")}); { "acknowledged" : true, "insertedId" : ObjectId("5cd6e8a86d78f205348bc62a") } > db.mongoDbSearchForHoursDemo.insertOne({"CustomerName":"Larry", "OrderDatetime":new ISODate("2019-02-21 01:10:01")}); { "acknowledged" : true, "insertedId" : ObjectId("5cd6e8b86d78f205348bc62b") } > db.mongoDbSearchForHoursDemo.insertOne({"CustomerName":"Larry", "OrderDatetime":new ISODate("2019-04-01 04:10:11")}); { "acknowledged" : true, "insertedId" : ObjectId("5cd6e8e26d78f205348bc62c") } > db.mongoDbSearchForHoursDemo.insertOne({"CustomerName":"Larry", "OrderDatetime":new ISODate("2019-05-11 08:53:01")}); { "acknowledged" : true, "insertedId" : ObjectId("5cd6e8f26d78f205348bc62d") }Following is the query to display all documents from a collection with the help of find() method −> db.mongoDbSearchForHoursDemo.find().pretty();This will ...
Read MoreC++ Program to Implement Affine Cipher
In the Affine cipher, each letter in an alphabet is mapped to its numeric equivalent, is a type of monoalphabetic substitution cipher. Encryption is done using a simple mathematical function and converted back to a letter.The letters of an alphabet of size m are first mapped to the integers in the range 0 … m-1, in the Affine cipher, The ‘key’ for the Affine cipher consists of 2 numbers, a and b. a should be chosen to be relatively prime to m.EncryptionTo transform the integer, it uses modular arithmetic that each plaintext letter corresponds to into another integer that correspond ...
Read MoreHow to declaring pointer variables in C/C++?
A pointer is used to store the address of the variables. To declare pointer variables in C/C++, an asterisk (*) used before its name.Declaration*pointer_nameIn CExample Live Demo#include int main() { // A normal integer variable int a = 7; // A pointer variable that holds address of a. int *p = &a; // Value stored is value of variable "a" printf("Value of Variable : %d", *p); //it will print the address of the variable "a" printf("Address of Variable : %p", p); // reassign the value. *p = 6; printf("Value ...
Read MoreC++ Program to Find the Shortest Supersequence that Contains Two or more Sequences as Subsequences
Here we shall discuss a C++ Program to find the Shortest Supersequence that contains two or more Sequences as Subsequences.AlgorithmBegin function ShortestSubSeq() returns supersequence of A and B: 1) Declare an array ss[i][j] which contains length of shortest supersequence for A[0 .. i-1] and B[0 .. j-1]. 2) Find the length of the possible supersequence in bottom up manner using recursion. 3) Declare an array ss[i][j] which stores length of shortest supersequence for A[0 .. i-1] and B[0 .. j-1] in index. 4) Declare a string s to store the shortest subsequence. 5) Initialize ...
Read MoreC++ Program to Find the Longest Prefix Matching of a Given Sequence
Here we shall discuss a C++ program to find the Longest Subsequence Common to All Sequences in a Set of Sequences.AlgorithmsBegin Take the array of strings as input. function matchedPrefixtill(): find the matched prefix between string s1 and s2 : n1 = store length of string s1. n2 = store length of string s2. for i = 0, j = 0 to i
Read MoreRAII and smart pointers in C++
RAII in C++RAII (Resource Acquisition Is Initialization) is C++ technique which control the life cycle of resource. It is a class variant and is tied to object life time.It encapsulates several resources into class where resource allocation is done by constructor during object creation and resource deallocation is done by destructor during object destruction.Resource is guaranteed to be held till the object is alive.Examplevoid file_write { Static mutex m; //mutex to protect file access lock_guard lock(m); //lock mutex before accessing file ofstream file("a.txt"); if (!file.is_open()) //if file is not open throw runtime_error("unable to open file"); ...
Read MoreHow to exclude _id without including other fields using the aggregation framework in MongoDB?
Let us first create a collection with documents −> db.excludeIdDemo.insertOne({"StudentFirstName":"John", "StudentAge":21}); { "acknowledged" : true, "insertedId" : ObjectId("5cd701a56d78f205348bc632") } > db.excludeIdDemo.insertOne({"StudentFirstName":"Robert", "StudentAge":20}); { "acknowledged" : true, "insertedId" : ObjectId("5cd701af6d78f205348bc633") } > db.excludeIdDemo.insertOne({"StudentFirstName":"Chris", "StudentAge":24}); { "acknowledged" : true, "insertedId" : ObjectId("5cd701b86d78f205348bc634") }Following is the query to display all documents from a collection with the help of find() method −> db.excludeIdDemo.find();This will produce the following output −{ "_id" : ObjectId("5cd701a56d78f205348bc632"), "StudentFirstName" : "John", "StudentAge" : 21 } { "_id" : ObjectId("5cd701af6d78f205348bc633"), "StudentFirstName" : "Robert", "StudentAge" : 20 } { "_id" : ObjectId("5cd701b86d78f205348bc634"), "StudentFirstName" : "Chris", "StudentAge" ...
Read MoreMeasure execution time with high precision in C/C++
To create high precision timer we can use the chrono library. This library has high resolution clock. This can count in nanoseconds.In this program we will see the execution time in nanoseconds. We will take the time value at first, then another time value at the last, then find the difference to get elapsed time. Here we are using blank loop to pause the effect for sometimes.Example#include #include typedef std::chrono::high_resolution_clock Clock; main() { auto start_time = Clock::now(); for(int i = 0; i
Read MoreIs it possible to achieve a slice chain in MongoDB?
Yes, you can achieve this using aggregate framework. Let us first create a collection with documents −> db.sliceOfSliceDemo.insertOne( ... { ... "Name": "John", ... "Details": [["First 1:1", "First 1:2"], ["second 2:1", "Second 2:2"]] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5ccf3fcfdceb9a92e6aa195a") }Following is the query to display all documents from a collection with the help of find() method −> db.sliceOfSliceDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5ccf3fcfdceb9a92e6aa195a"), "Name" : "John", "Details" : [ [ "First ...
Read MoreUpdate Array element in MongoDB?
Use $addToSet operator to update array element. Let us first create a collection with documents −> db.updateArrayDemo.insertOne( ... { ... ... "ClientDetails" : [ ... { ... "ClientName" : "John", ... "DeveloperDetails" : [ ] ... }, ... { ... "ClientName" : "Larry", ... "DeveloperDetails" : [ ] ... } ... ] ... ...
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