Find consecutive elements in list that match expression

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I would like to retrieve the elements from a list that (in consecutive order) match an expression, but for the moment I don't see the (performant) solution.

E.g.:

var items = new List<string>
{
   "1",
   ".",
   "249",
   "something",
   "1", // 5
   ".", // 6
   "250", // 7
   "yes"
};

// I am looking for the consecutive elements that form the expression below (5-6-7).
var match = "1.250";
var elements = ...;

Here's a way that's straightforward and isn't nested more than 1 level.

This will find the first match. If no match is found, indexes will have a count of 0 after the loop. Put inside a method of your choosing.

List<int> indexes = new List<int>();
for (int i = 0; i < items.Count; i++)
{
    string temp = items[i];
    while (temp.Length < match.Length && temp == match.Substring(0, temp.Length) && i < items.Count - 1)
    {
        indexes.Add(i + 1); // example was given using 1-based
        temp += items[++i];
    }

    if (temp == match)
    {
        indexes.Add(i + 1);
        break; // at this point, indexes contains the values sought
    }

    indexes.Clear();
}

With a list of 10,000 elements, where the elements to find are at the end, this runs in about 0.0003775 seconds.

Identify if list has consecutive elements that are equal in python , You can use itertools.groupby() and a generator expression within any() *: >>> from itertools import groupby >>> any(sum(1 for _ in g) > 1 for _,  Python | Consecutive elements pairing in list Sometimes, while working with lists, we need to pair up the like elements in the list and then store them as lists of lists. This particular task has its utility in many domains, be it web development or day-day programming.

This should give an answer but if there is more than one matches it returns the last one.

 public static void GetConsecutiveMatch(List<String> items, String match, out List<int> indices)
    {
        indices = new List<int>();
        for (int i = 0; i < items.Count(); i++)
        {
            var strToCompare = "";
            for (int j = i ;  j < items.Count(); j++)
            {
                strToCompare += items[j];
                if (strToCompare.Length == match.Length)
                {
                    if (strToCompare == match)
                    {
                        indices.Clear();
                        for (int k = i; k <= j; k++)
                        {
                            indices.Add(k + 1); // at your example indices seems to be starting at 1, so I added 1 to the actual index
                        }
                    }

                    break;              
                }
                else if (strToCompare.Length > match.Length)
                {
                    break;
                }
            }
        }
    }

Python, Sometimes, while working with lists, we need to pair up the like elements in the list and then store them as lists of lists. This particular print ( "The consecutive element paired list is : " + str (res)) first_page Python | Get match indices. Next. Sometimes, while working with Python list, we have a problem in which we have to search for a element in list. But this can be extended to a list and need to find the exact places where elements occur in other list. Let’s discuss certain ways in which this task can be performed. Method #1 : Using loop + count()

Try IEquatable :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;


namespace ConsoleApplication137
{
    class Program
    {
        static void Main(string[] args)
        {
            List<string> ipAddresses = new List<string>() {
                "172.15.15.1",
                "172.15.15.2",
                "172.15.15.3",
                "172.15.15.4",
                "172.16.15.1",
                "172.17.15.1"
            };

            MatchIp matchIP = new MatchIp("172.15", "172.16");
            List<string> results = ipAddresses.Where(x => matchIP.Equals(x)).ToList();
        }
    }
    public class MatchIp : IEquatable<string>
    {
        int[] startAddress { get; set; }
        int[] endAddress { get; set; }
        int length { get; set; }

        public MatchIp(string startAddressStr, string endAddressStr)
        {
            startAddress = startAddressStr.Split(new char[] { '.' }).Select(x => int.Parse(x)).ToArray();
            endAddress = endAddressStr.Split(new char[] { '.' }).Select(x => int.Parse(x)).ToArray();
            length = Math.Min(startAddress.Count(), endAddress.Count());
        }

        public Boolean Equals(string ip)
        {
            Boolean results = true;

            try
            {
                int[] address = ip.Split(new char[] { '.' }).Select(x => int.Parse(x)).ToArray();
                if (address.Length == 4)
                {
                    for (int i = 0; i < length; i++)
                    {
                        if ((address[i] < startAddress[i]) || (address[i] > endAddress[i]))
                        {
                            results = false;
                            break;
                        }
                    }
                }
                else
                {
                    results = false;
                }
            }
            catch (Exception ex)
            {
                results = false;
            }

            return results;
        }
    }

}

Find subsequences of consecutive integers inside a list , You can use Split in this simple case list = {3, 4, 5, 6, 7, 10, 11, 12, 15, 16, 17, 19, 20, 21, 22, 23, 24, 42, 43, 44, 45, 46}; {Min[#], Max[#]} & /@ Split[list, #2 - #1  Regex to match same consecutive characters If you are a coder on Python/Per/Ruby/PHP then using regular expression will boost your coding speed a lot. *" will match any character inbetween them. For example, if the word to be checked is word list and this setting is set to 6, then the system checks these combinations wordli, ordlis, and rdlist

  public IEnumerable<int> GetMatch(List<string> items, string match)
  {
     string str = null;
     for (int i = 0; i < items.Count; i++)
     {
        if (!match.StartsWith(items[i]))
           continue;
        for (int j = 1; j < items.Count - i + 1; j++)
        {
           str = items.Skip(i).Take(j).Aggregate((x, y) => x + y);
           if (str.Equals(match))
              return Enumerable.Range(i + 1, j).Select(x => x).ToList();
           else if (match.StartsWith(str))
              continue;
           break;
        }
     }
     return new int[0];
  }



  [Fact]
  public void Test()
  {
     var items = new List<string> { "1", ".", "249", "something", "1", ".", "250", "yes" };
     var match = "1.250";
     var matchingIndexes = GetMatch(items, match);
     Assert.True(matchingIndexes.Any());
     Assert.Equal(5, matchingIndexes.ElementAt(0));
     Assert.Equal(6, matchingIndexes.ElementAt(1));
     Assert.Equal(7, matchingIndexes.ElementAt(2));
  }

Python check if list has consecutive numbers, Code #1 : Demonstrating to check existence of element in list using Naive you need to search for just 'cat' or some other regular expression and return a list of  Consecutive Repeating Characters Regex Matches any character except new line (). [bc-] The characters b, c or - (dash). A ' character followed by any single character which is neither ' nor a newline.

Professional C++, Here are examples of some of the search algorithms: // The list of elements to be Find the first element that does not satisfy the given lambda expression auto it 8 is " << *it << endl; } // Find the first pair of matching consecutive elements it  Here we consider the Find() method on List. Find accepts a Predicate, which we can specify as a lambda expression. It returns the first match.Predicate Lambda. Here: This code loops through each int value in the List, starting at the beginning, and tests each one to see if it is greater than 20. Return: The value 23 is returned. The parameter to the Find method is a lambda expression: a Predicate instance.

Python check if list has consecutive numbers, Python in is the most conventional way to check if an element exists in list or not. or some other regular expression and return a list of the list items that match,  The simple way to search for a string in a list is just to use ‘if string in list’. eg: But what if you need to search for just ‘cat’ or some other regular expression and return a list of the list items that match, or a list of selected parts of list items that … Continue reading Python: Searching for a string within a list – List comprehension →

NASA Formal Methods: Third International Symposium, NFM 2011, , Expressing the initial state constraint is easy, since the first element of the list is two consecutive elements of the list, we first define an uninterpreted function, that “traverses” the whole list, we decided to include the safety property check in  Regular expressions are a tool for matching text patterns in strings of varying length and content. Regexes give you the flexibility to run searches on/match patterns beyond literal fixed characters. The Python module that provides Regex support is called “re”. Search with the re.search() method:

Comments
  • Are the pieces always split up in the same manner?
  • Could the post include the code that's been tried?
  • Also, in the example given, are you looking for "5,6,7" or "4,5,6" (1-based vs 0-based counting)?
  • @elmer007 Indeed if you go 0-based counting it's 4,5,6, that is why I added the comments 5-6-7 to be sure everybody would be aligned. :-)
  • @juharr No they are not always split up in the same manner. Could be that the 250 would be split over multiple records or that you'd even just have 1 element in the list for 1.250
  • Thanks! Very nice solution. I still added a check in the while loop to ensure the index does not go out of range.
  • That makes sense. I've edited to include that condition now.