Logic to check 3 consecutive sequence

Deer Park

So, I have a list of integers say -
set one - 1,2,3,22,34,21
set two - 2,4,5,3,7,8
set three - 5,9,8,1,2,3

I have a function which should return true or false based on if the list contains consecutive three sequence number. So the set one and set three mentioned above should return true if passed to the function since those set have 3 numbers in sequence consecutively.

What the elegent way to do this? is it better to do it by checking each element of the array or is there a way to get this using Linq?
Please suggest.

6 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes14y ago
Accepted answer
A more specific approach:

using System;
using System.Collections.Generic;

class Test
{
static void Main()
{
var set1 = new List { 1, 2, 3, 22, 34, 21 };
var set2 = new List { 2, 4, 5, 3, 7, 8 };
var set3 = new List { 5, 9, 8, 1, 2, 3 };
var set4 = new List { 1, 2, 3 };
Console.WriteLine("Set1 = {0}", ContainsSequenceOf3(set1));
Console.WriteLine("Set2 = {0}", ContainsSequenceOf3(set2));
Console.WriteLine("Set3 = {0}", ContainsSequenceOf3(set3));
Console.WriteLine("Set4 = {0}", ContainsSequenceOf3(set4));
Console.ReadKey();
}

static bool ContainsSequenceOf3(List set)
{
if (set.Count < 3) return false;

for(int i = 0; i < set.Count - 2; i++)
{
if( set[i+1] == set[i] + 1 && set[i+2] == set[i] + 2) return true;
}

return false;
}
}
Deer Park14y ago
Thanks Vulpes! Appreciated.
Deer Park14y ago
Thanks Bicca. I really appreciate your help on this.
Deer Park14y ago
Thank you so much. Really Appreciated.
Bicca14y ago
My 2 cents on this:

static bool HasSequence(List lst, int MaxSequence)
{
int CounterHit = 0;
int MaxHit = MaxSequence - 1;

for (int idx = 0; idx < lst.Count - 1; idx++)
{
if (lst[idx] == lst[idx + 1] - 1)
{
CounterHit++;
if (CounterHit == MaxHit)
return true;
}
else
CounterHit = 0;
}

return false;
}
Felipe Ramos14y ago
In the following code, the three sets will return true because set two contains 2,3,4,5. This may not be the best way, but it is a solution that can lead to better implementations.

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

namespace Answers
{
class Program
{
static void Main(string[] args)
{
List set1 = new List { 1, 2, 3, 22, 34, 21 },
set2 = new List { 2, 4, 5, 3, 7, 8 },
set3 = new List { 5, 9, 8, 1, 2, 3 },
set4 = new List { 1, 2, 3 };

Console.WriteLine(set1.ContainSequence());
Console.WriteLine(set2.ContainSequence());
Console.WriteLine(set3.ContainSequence());
Console.WriteLine(set4.ContainSequence());
Console.ReadKey();
}
}

public static class Extensions
{
public const int MIN_SEQUENCE = 3;

public static bool ContainSequence(this List set, int minSequence = MIN_SEQUENCE)
{
set = set.Distinct().OrderBy(o => o).ToList();

int match = 0;

if (set.Count >= minSequence)
for (int x = 0; x < set.Count; x++)
{
if (x + 1 <= set.Count - 1)
if (set[x] + 1 == set[x + 1])
match += 1;
else if (set[x] - 1 == set[x - 1])
match += 1;
else
match = 0;
else if (set[x] - 1 == set[x - 1])
match += 1;

if (match >= minSequence)
return true;
}

return false;
}
}
}