C#: Check whether the sequence of numbers 1, 2, 3 appears in a given array of integers somewhere

Last update on June 25 2025 13:03:52 (UTC/GMT +8 hours)

Check Sequence 1, 2, 3 in Array

Write a C# Sharp program to check whether the sequence of numbers 1, 2, 3 appears in a given array of integers somewhere.

Visual Presentation:

Sample Solution:-

C# Sharp Code:

using System;
using System.Linq;

// Namespace declaration
namespace exercises
{
    // Class declaration
    class Program
    {
        // Main method - entry point of the program
        static void Main(string[] args)
        {
            // Calling the 'test' method with different integer arrays
            Console.WriteLine(test(new[] {1,1,2,3,1}));   // Output: True
            Console.WriteLine(test(new[] {1,1,2,4,1}));   // Output: False
            Console.WriteLine(test(new[] {1,1,2,1,2,3})); // Output: True
            Console.ReadLine(); // Keeping the console window open
        }   

        // Method to check if an array contains the sequence 1, 2, 3 in consecutive positions
        public static bool test(int[] nums)
        {
            // Loop through the array elements except the last two
            for (var i = 0; i < nums.Length-2; i++)
            {
                // Check if the current element and the next two elements form the sequence 1, 2, 3
                if (nums[i] == 1 && nums[i + 1] == 2 && nums[i + 2] == 3)
                    return true; // Return true if the sequence is found
            }

            return false; // Return false if the sequence is not found
        }
    }
}

Sample Output:

True
False
True

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C# program to detect any ascending sequence of 3 consecutive integers in a given array.
• Write a C# program to check if the sequence 1,2,3 exists in reverse order anywhere in the array.
• Write a C# program to determine if multiple non-overlapping sequences of 1,2,3 exist in an array.
• Write a C# program to check if the sequence 1,2,3 appears starting from an even index.

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