想要找到最高最大数和第二大最大数及其索引值

Question

This code finds the highest number and second highest number but gives the wrong index number, but only in some cases When array values: {1,3,3,0,3} When Array Values: {3,3,0,1,2}

If all are unique numbers then it gives an accurate answer with accurate index value; Where do I need to change the code to get accurate index value for above cases?

FirstMaxNumber=arrFindIndex[0];
SecondMaxNumber=arrFindIndex[0];
FirstMaxRatingIndex=0;
SecondMaxRatingIndex=0;

for (int i = 0; i < arrSize; i++)
{
     if (FirstMaxNumber <= arrFindIndex[i])
     {
         SecondMaxNumber = FirstMaxNumber;
         FirstMaxNumber = arrFindIndex[i];
         FirstMaxRatingIndex = i;
      }
      else if (SecondMaxNumber <= arrFindIndex[i])
      {
         SecondMaxNumber = arrFindIndex[i];
         SecondMaxRatingIndex = i;
      }
}

// print(FirstMaxNumber);
// Print(FirstMaxRatingIndex);

// print(SecondMaxNumber);
// print(SecondMaxRatingIndex);

Answer 1

In the first if statement, the value of the second maximum value is set:

SecondMaxNumber = FirstMaxNumber;

but the index isn't:

SecondMaxRatingIndex = FirstMaxRatingIndex;
FirstMaxRatingIndex = i;

Answer 2

Something like this:

FirstMaxNumber = arrFindIndex[0];
SecondMaxNumber = arrFindIndex[0];

FirstMaxRatingIndex = 0;
SecondMaxRatingIndex = 0;

// Do not use magic values: "arrSize" but actual length: arrFindIndex.Length
for (int i = 1; i < arrFindIndex.Length; i++) {
  int v = arrFindIndex[i];

  if (v > FirstMaxNumber) {
    // so "first" becomes "second"
    SecondMaxNumber = FirstMaxNumber;
    SecondMaxRatingIndex = FirstMaxRatingIndex;

    FirstMaxNumber = v;
    FirstMaxRatingIndex = i;
  }
  else if ((v > SecondMaxNumber) || (i == 1)) {
    SecondMaxNumber = v;
    SecondMaxRatingIndex = i;
  }
}

Answer 3

Why don't you just use LINQ for that?

var arr = new [] {3, 0, 4, 2, 3, 7};
var min = arr.Select((Val, Key) => new { Val, Key }).First(x => x.Val == arr.Min());
var max = arr.Select((Val, Key) => new { Val, Key }).First(x => x.Val == arr.Max());

Console.WriteLine($"Min Key: {min.Key} Val: {min.Val} \nMax Key: {max.Key} Val: {max.Val}");

// Output
// Min Key: 1 Val: 0 
// Max Key: 5 Val: 7

Answer 4

If the arrays are short and you don't particularly care how fast it is, the easiest code is something like this:

var indices = Enumerable.Range(0, array.Length).ToArray();
Array.Sort(array, indices, Comparer<int>.Create((a, b) => b - a));

Then indices will contain the indices of all the elements, in descending order, so you just need the first two.

Here's a compilable console app (requires .Net 4.5 or later):

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

namespace Demo
{
    static class Program
    {
        static void Main()
        {
            test(1, 3, 3, 0, 3); // Prints 1, 2
            test(3, 3, 0, 1, 2); // Prints 0, 1
        }

        static void test(params int[] array)
        {
            var indices = Enumerable.Range(0, array.Length).ToArray();
            Array.Sort(array, indices, Comparer<int>.Create((a,b)=>b-a));
            Console.WriteLine($"{indices[0]}, {indices[1]}");
        }
    }
}