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Articles on Trending Technologies
Technical articles with clear explanations and examples
The Substitution Operator in Perl
The substitution operator s/// in Perl is really just an extension of the match operator that allows you to replace the text matched with some new text. The basic form of the operator is −s/PATTERN/REPLACEMENT/;The PATTERN is the regular expression for the text that we are looking for. The REPLACEMENT is a specification for the text or regular expression that we want to use to replace the found text with. For example, we can replace all occurrences of dog with cat using the following regular expression −Example#/user/bin/perl $string = "The cat sat on the mat"; $string =~ s/cat/dog/; print "$string";When the above program is ...
Read MoreFind All Duplicate Subtrees in C++
Consider we have a binary tree. We have to find if there are some duplicate subtrees in the tree or not. Suppose we have a binary tree like below −There are two identical subtrees of size 2. In each subtree D, BD and BE both are also duplicate subtrees We can solve this problem by using tree serialization and hashing process. We will store the inorder traversal of subtrees in the hash table. We will insert opening and closing parenthesis for empty nodes.Example#include #include #include #include using namespace std; const char MARKER = '$'; struct Node ...
Read MoreFind all factorial numbers less than or equal to n in C++
Here we will see how to print all factorial numbers less than or equal to n, a number N is said to be factorial number if it is a factorial of a positive number. So some factorial numbers are 1, 2, 6, 24, 120.To print factorial numbers, we do not need to find the factorial directly. Starting from i = 1, print factorial*i. Initially factorial is 1. Let us see the code for better understanding.Example#include using namespace std; void getFactorialNumbers(int n) { int fact = 1; int i = 2; while(fact
Read MoreFind all pairs (a, b) in an array such that a % b = k in C++
Suppose we have an array A, from that array, we have to get all pairs (a, b) such that the a%b = k. Suppose the array is A = [2, 3, 4, 5, 7], and k = 3, then pairs are (7, 4), (3, 4), (3, 5), (3, 7).To solve this, we will traverse the list and check whether the given condition is satisfying or not.Example#include using namespace std; bool displayPairs(int arr[], int n, int k) { bool pairAvilable = true; for (int i = 0; i < n; i++) { for (int j = 0; j < n; j++) { if (arr[i] % arr[j] == k) { cout
Read MoreGrouping Matching in Perl
From a regular-expression point of view in Perl, there is no difference between the following two expressions except that the former is slightly clearer.$string =~ /(\S+)\s+(\S+)/; and $string =~ /\S+\s+\S+/;However, the benefit of grouping is that it allows us to extract a sequence from a regular expression. Groupings are returned as a list in the order in which they appear in the original. For example, in the following fragment we have pulled out the hours, minutes, and seconds from a string.my ($hours, $minutes, $seconds) = ($time =~ m/(\d+):(\d+):(\d+)/);As well as this direct method, matched groups are also available within the ...
Read MoreFind all pairs (a,b) and (c,d) in array which satisfy ab = cd in C++
Suppose we have an array A, from that array, we have to choose two pairs (a, b) and (c, d), such that ab = cd. Let the array A = [3, 4, 7, 1, 2, 9, 8]. The output pairs are (4, 2) and (1, 8). To solve this, we will follow these steps −For i := 0 to n-1, dofor j := i + 1 to n-1, doget product = arr[i] * arr[j]if product is not present in the hash table, then Hash[product] := (i, j)if product is present in the hash table, then print previous and current elements.Example#include ...
Read MoreThe G Assertion in Perl
The \G assertion in Perl allows you to continue searching from the point where the last match occurred. For example, in the following code, we have used \G so that we can search to the correct position and then extract some information, without having to create a more complex, single regular expression −Example#!/usr/bin/perl $string = "The time is: 12:31:02 on 4/12/00"; $string =~ /:\s+/g; ($time) = ($string =~ /\G(\d+:\d+:\d+)/); $string =~ /.+\s+/g; ($date) = ($string =~ m{\G(\d+/\d+/\d+)}); print "Time: $time, Date: $date";When the above program is executed, it produces the following result −Time: 12:31:02, Date: 4/12/00The \G assertion is actually ...
Read MoreFind amount to be added to achieve target ratio in a given mixture in C++
Suppose we have a container with size X. It has a mixture of water and other liquid, the mixture has W% of water in it. We have to find how many water must be added to increase the ratio of water to Y%? If X = 125, W = 20 and Y = 25, then output will be 8.33 liters.Suppose we have to add A amount of water with the previous mixture, so new amount will be X + A. So the amount of water in the mixture will follow this formula.Old Amount+A=((W% of X) + A)Also the amount of ...
Read MoreFind a local minima in an array in C++
Suppose we have an array A with n elements. We have to find the local minima of the array. In array A, the element A[x] is said to be local minima if it is less than or equal to both of its neighbors. For corner elements only one neighbor will be considered. And if there are more than one local minima available, then return only one. For example, if the array is like [9, 6, 3, 14, 5, 7, 4], then the local minima can be 3, 5 and 4, so this algorithm can return only one of them.To solve ...
Read MoreFind a permutation of 2N numbers such that the result of given expression is exactly 2K in C++
Suppose we have two integers N and K. We have to find first permutation of 2N number of natural numbers, such that the following equation is satisfied.$$\displaystyle\sum\limits_{i=1}^N\lvert A_{2i-1}-A_{2i}\rvert+\lvert \displaystyle\sum\limits_{i=1}^N A_{2i-1}-A_{2i} \rvert=2K$$The value of K should be less than or equal to N. For example, if N = 4 and K = 1, then output will be 2 1 3 4. The result of the given expression will be (|2 – 1| + |3 – 4|) – (|2 – 1 + 3 – 4|) = 2.The idea is simple, consider we have a sorted sequence like 1, 2, 3, 4, 5, ...
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