持续崩溃，如果有条件

Question

So I am kind of new to programming (16 y/o) and I have been solving problems for a while now, but now I am solving this one prob (which is quite easy) there seems to be just one thing getting on my way. The problem is pretty simple, it only needs me to read 3 integers and print out the greatest one, I have already solved it in C++/C and had no problem, at all. But this one, It prints out and works perfectly when the first two if conditions are true (if a is the greatest value, it prints a, if b is the greatest value it prints b) but when c is the greatest value it comes out empty. Sorry for the long post, hope someone can help me out.

using System;


namespace MaxP351
{
    class MainClass
    {
        public static void Main (string[] args)
        {
            string[] input = Console.ReadLine ().Split (' '); // getting input as string
            int[] nums = new int[input.Length]; // declaring int array with same length as input
            for (int i = 0; i < input.Length; i++) { // starting a for loop to convert input string to int in nums[]
                nums[i] = Convert.ToInt32(input[i]);
            }
            int a, b, c;
            a = nums [0];
            b = nums [1];
            c = nums [2];
            if (a > b && a > c) {
                Console.WriteLine (a);
                break;
            } else if (b > a && b > c) {
                Console.WriteLine (b);
                break;
            } else if (c > a && c > b) {
                Console.WriteLine (c);
                break;
            } 

     }
}

Answer 1

If c is truly the largest number then your code should be printing out the value for c . If this were my code, I would set a break point at your if statement and see what the values are. Alternatively you can print out the values of a,b and c right before your if statements and make sure they are the values that you expect. Example:

Console.WriteLine("Values before if statement:")
Console.WriteLine (a);
Console.WriteLine (b);
Console.WriteLine (c);
if (a > b && a > c) {
...

Again - I would recommend going the breakpoint route, but the above might be a quick and dirty way to see the values if you aren't familiar with visual studio debugging.

In summary - your code should give you the desired output. The problem most likely lies somewhere else.

Answer 2

1. No need break; for if-else statements.

2. No need if statements at all to display the largest integer. You can do below.

 Console.WriteLine(nums.Max())

3. If you don't want to use Max function. Do a proper loop which is better than too many if conditions;

    int? maxVal = null; // ? means nullable int. Set null just to initialize

    for (int i = 0; i < nums.Length; i++)
    {
      int currentNum = nums[i];
      if (!maxVal.HasValue || currentNum > maxVal.Value)
      {
        maxVal = currentNum;
      }
    }

   Console.WriteLine(maxVal);

Answer 3

You dont need a 'break' as you are using if-else if. Below should help

if (a > b && a > c) {
    Console.WriteLine (a);
} else if (b > a && b > c) {
    Console.WriteLine (b);
} else {
    Console.WriteLine (c);
} 

Answer 4

Your if statements do not handle the numbers with same value

Correct as below:

if (a >= b && a >= c) {
    Console.WriteLine (a);
    //break;
} else if (b >= a && b >= c) {
    Console.WriteLine (b);
    //break;
} else {
    Console.WriteLine (c);
    //break;
} 

Answer 5

Try this

static void Main(string[] args)
    {
        try
        {
            Console.WriteLine("Input first number: ");
            var a = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine("Input second number: ");
            var b = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine("Input third number: ");
            var c = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine(a);
            Console.WriteLine(b);
            Console.WriteLine(c);
            if (a > b && a > c)
            {
                Console.WriteLine(a);
            }
            else if (b > a && b > c)
            {
                Console.WriteLine(b);
            }
            else if (c > a && c > b)
            {
                Console.WriteLine(c);
            }                
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
        Console.ReadKey();
    }

Edit: If you make it dynamic then

static void Main(string[] args)
    {
        try
        {
            Console.WriteLine("Enter numbers (Example 25,46,19)");
            var input = Console.ReadLine();
            if (input == null)
            {
                Console.WriteLine("Your input is wrong");
                return;
            }
            var numbers = input.Split(',');
            //Sort by descending order
            for (int i = 0; i < numbers.Length; i++)
            {
                for (int j = 0; j < numbers.Length - 1; j++)
                {
                    if (Convert.ToInt32(numbers[i]) > Convert.ToInt32(numbers[j]))
                    {
                        var temp = Convert.ToInt32(numbers[i]);
                        numbers[i] = numbers[j];
                        numbers[j] = temp.ToString();
                    }
                }
            }
            Console.WriteLine("Greater Number is {0}", numbers[0]);                
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
        Console.ReadKey();
    }

Answer 6

I executed your code it works properly if break is removed. there is no loop for the break statement to break and continue.it gives a compilation error. Remove that and it gives the correct result.

http://i.imgur.com/O02akZx.jpg here is the screen shot

Answer 7

Adding break; inside if/else blocks won't let your code compile :) After fixing this, your if/else code block in itself, looks correct. I tested it and it prints out c in my machine.

To answer your question related to If statements , if I were you, I would check:

• If c is really the greatest (it may be greater than a, but not b, then it fails)
• Unwanted space before or after c (maybe failing the conversion? You can try trimming string before conversion.)

This is neater if you can use .Max():

    public static void Main(string[] args)
    {
        string[] input = Console.ReadLine().Split(' '); // getting input as string            
        List<int> nums = new List<int>(); // declaring int array with same length as input
        for (int i = 0; i < input.Length; i++) // starting a for loop to convert input string to int in nums[]
        {                
            int intValue;
            if (Int32.TryParse(input[i].Trim(), out intValue))
            {
                nums.Add(intValue);
            }
        }

        int max = nums.Max();
        int min = nums.Min();

        Console.WriteLine("Largest: " + max);
        Console.WriteLine("Smallest: " + min);

        Console.WriteLine("Press Enter to exit.");
        Console.ReadLine();
    }

This is without .Max():

    public static void Main(string[] args)
    {
        string[] input = Console.ReadLine().Split(' '); // getting input as string            
        List<int> nums = new List<int>(); // declaring int array with same length as input
        for (int i = 0; i < input.Length; i++) // starting a for loop to convert input string to int in nums[]
        {                
            int intValue;
            if (Int32.TryParse(input[i].Trim(), out intValue))
            {
                nums.Add(intValue);
            }
        }

        //int max = nums.Max();
        //int min = nums.Min();

        int min = nums[0];
        int max = nums[0];
        for (int i = 0; i < nums.Count(); i++)
        {
            if (nums[i] < min) min = nums[i];
            if (nums[i] > max) max = nums[i];
        }

        Console.WriteLine("Largest: " + max);
        Console.WriteLine("Smallest: " + min);

        Console.WriteLine("Press Enter to exit.");
        Console.ReadLine();
    }

Note:

• List<int> was used to accommodate user adding more than 3 values.

• Avoided using a, b, c so that the program can accept more than 3 values.

• Used Int32.TryParse(your_string, out outputInt) to conveniently detect parse errors and move on. Use .Trim() to remove spaces before and after each text block.