How to stop a for loop at a specific cycle?

Question

Hello,

I am trying to stop a loop at a specific cycle.

using System.CodeDom.Compiler;
using System.Collections.Generic;
using System.Collections;
using System.ComponentModel;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.Serialization;
using System.Text.RegularExpressions;
using System.Text;
using System;

class Solution {

    // Complete the maxSubsetSum function below.
    static int maxSubsetSum(int[] arr) {

         int size = arr.Length;
        int max_so_far = int.MinValue,
         max_ending_here = 0; 

        for (int i = 0; i < size; i++) 
        {

            if (i % 2 == 0)
            {

            max_ending_here = max_ending_here + arr[i];


            if (max_so_far < max_ending_here)
                max_so_far = max_ending_here;

            // cant tell why the loop not stopping at the largest sum

                 Console.WriteLine("\t3rd loop cycle!:  " +max_ending_here );
            }

        }


        return max_so_far;

    }

    static void Main(string[] args) {
        TextWriter textWriter = new StreamWriter(@System.Environment.GetEnvironmentVariable("OUTPUT_PATH"), true);

        int n = Convert.ToInt32(Console.ReadLine());

        int[] arr = Array.ConvertAll(Console.ReadLine().Split(' '), arrTemp => Convert.ToInt32(arrTemp))
        ;
        int res = maxSubsetSum(arr);

        textWriter.WriteLine(res);

        textWriter.Flush();
        textWriter.Close();
    }
}

The output return :

Input (stdin)

5

3 7 4 6 5

Your Output (stdout)

12

Expected Output

13

Debug output

 3rd loop cycle!:  3

 3rd loop cycle!:  7

 3rd loop cycle!:  12


5

3 5 -7 8 10

Your Output (stdout)

6

Expected Output

15

Debug output

 3rd loop cycle!:  3

 3rd loop cycle!:  -4

 3rd loop cycle!:  6


5

2 1 5 8 4

Only this output return the right answer.

Your Output (stdout)

11

Expected Output

11

Debug output

 3rd loop cycle!:  2

 3rd loop cycle!:  7

 3rd loop cycle!:  11

Thank you

Answer 1

Use a break when the condition is hit e.g.

var breakOn = 9;

for (int index = 0; index < 22; index++)
{

    if (index == breakOn)
    {
        Console.WriteLine($"Breaking on {breakOn}");
        break;
    }
    Console.WriteLine($"{index}");
}

Another example

int[] breakItems = {11, 15, 19};

for (int index = 0; index < 22; index++)
{

    if (breakItems.Contains(index))
    {
        Console.WriteLine($"Breaking on {index}");
        break;
    }
    Console.WriteLine($"{index}");
}

Or

for (int index = 0; index < 22; index++)
{

    switch (index)
    {
        case 11:
            Console.WriteLine("\t11");
            break;
            case 15:
                Console.WriteLine("\t15");
                break;
            case 19:
                Console.WriteLine("\t19");
                break;
            default:
                Console.WriteLine(index);
                break;
    }

}


bool breakOut = false;
for (int index = 0; index < 22; index++)
{

    switch (index)
    {
        case 11:
            Console.WriteLine("\t11");
            breakOut = true;
            break;
        case 15:
            Console.WriteLine("\t15");
            breakOut = true;
            break;
        case 19:
            Console.WriteLine("\t19");
            breakOut = true;
            break;
        default:
            Console.WriteLine(index);
            break;
    }

    if (breakOut)
    {
        break;
    }

}

If this was in a method and wanted to return a value we use return. Also look at continue

Or multiple cases

private static bool BreakOutWithoutExpression(in int index)
{
    var result = false;

    switch (index)
    {
        case 11:
        case 15:
        case 19:
            result = true;
            break;
    }

    return result;
}

See also
https://kodify.net/csharp/loop/exit-loop/

Answer 2

If using the current release or C#8 then there are switch expressions

private static bool BreakOut(int index) => index switch {11 => true, 15 => true, 19 => true, _ => false};

.

for (int index = 0; index < 22; index++)
{
    if (!BreakOut(index)) continue;
    Console.WriteLine(index);
    break;
}