Summing up distinct elements in steps

In addition to the comments in Heslacher answer, I have few more notes on your code:

• remove lines instead of commenting them. What's the use of lines such as //using System.Linq;? You're not going to use it, so you don't even need to mention it.
• try to avoid using static variables and replace them with instance variables. Having an instance-local state is much better and will help your code to be much easier to extend and/or reuse.

I also noticed this comment //remove not all code paths return.. error and it is a bit of a red flag to me. It is the only return statement in that method so you should have it to actually return something, not only to make the compiler happy.

In my opinion, the real problem you have with your algorithm is the number of time you go through your array. Going through it only once would bring better performance. I'd have a hard time explaining what I changed without showing you how I rewrote your algo. I decided to add all the values, since you can't know what is the highest/lowest score until you finished looping the array, then substract the highest/lowest score (more than once if needed).

 public int CalculateScore(int[] scores) { int lowestValue = int.MaxValue, highestValue = int.MinValue, ammountOfHighestValue = 1, ammountOfLowestValue = 1, finalScore = 0; foreach (int score in scores) { finalScore += score; if (score < lowestValue) { lowestValue = score; ammountOfLowestValue = 1; //We need to reset the ammount } else if (score > highestValue) { highestValue = score; ammountOfHighestValue = 1; //We need to reset the ammount } else if (score == lowestValue) ammountOfLowestValue++; else if (score == highestValue) ammountOfHighestValue++; } if (ammountOfHighestValue > 1) //This way, we keep the highest score once. finalScore -= ((ammountOfHighestValue - 1) * highestValue); else finalScore -= highestValue; //The value is there once, we remove it. if (ammountOfLowestValue > 1) finalScore -= ((ammountOfLowestValue - 1) * lowestValue); //Same as highest else finalScore -= lowestValue; return finalScore; } 

Note that this answer is far from the best in a OOP point of view, but I think in performance it would be better since you have a O(n) complexity.

I figured out how I would do this and did it step by step, much like I assume that you have done it. I like to build things rather than destroy them, so I started at the beginning of the problem

First, I created methods to get the highest value and the lowest value.

I used a foreach instead of trying to use indexes which allowed me to make it clearer what was going on as well. I used a ternary statement inside of each method because I like the way they look as opposed to if then statements, I turned your if then statements into these ternary statements, they produce the same result, if you are not allowed to use them you can insert your if then statements in here.

 static int getHighestScore(int[] integerArray) { var high = 0; foreach (int number in integerArray) { high = high < number ? number : high; } return high; } static int getLowestScore(int[] integerArray) { var low = int.MaxValue; foreach (int number in integerArray) { low = low > number ? number : low; } return low; } 

This way I can just get the high number and the low number should I need them for something, and I can take this method out of the program and insert it into others should I need something like this in the future.

Note: If we are going to be dealing with Negative numbers we would need to change the getHighestScore method it account for that, so instead of

var high = 0; 

we would have:

var high = int.MinValue; 

Then I decided that I wanted the sum with our the highest and the lowest numbers, so I created another method that would sum the values of the array if they were not the highest or lowest value.

What I did here was add all the numbers of the array unless they were the high and low numbers.

static int sumWithoutHighAndLowScores(int[] integerarray) { int sum = 0; int high = getHighestScore(integerarray); int low = getLowestScore(integerarray); foreach (int number in integerarray) { if (number != high && number != low) { sum += number; } } return sum; } 

Now this doesn't tell me the sum if I have more than 1 high or low number, so what I did was count the high numbers and the low numbers and then if there is more than one I added it once to the sum.

static int sumWithoutHighAndLowScores(int[] integerarray) { int sum = 0; int high = getHighestScore(integerarray); int low = getLowestScore(integerarray); foreach (int number in integerarray) { if (number != high && number != low) { sum += number; } } return sum; } 

I didn't see an example/test case where there was multiple values that were not the high or the low, so I haven't coded for that scenario.

I may attempt a version that only counts unique numbers and high/low(if there is more than one) later.

Here is the full code and implementation.

static void Main(string[] args) { // take an array and sum the distinct numbers int[] numberArray = { 4, 8, 6, 4, 8, 5 }; int[] numberArray2 = { 4, 4, 5, 6, 8, 8 }; Console.WriteLine(sumSpecial(numberArray).ToString()); Console.WriteLine(sumSpecial(numberArray).ToString()); Console.ReadLine(); } static int getHighestScore(int[] integerArray) { var high = 0; foreach (int number in integerArray) { high = high < number ? number : high; } return high; } static int getLowestScore(int[] integerArray) { var low = int.MaxValue; foreach (int number in integerArray) { low = low > number ? number : low; } return low; } static int sumWithoutHighAndLowScores(int[] integerarray) { int sum = 0; int high = getHighestScore(integerarray); int low = getLowestScore(integerarray); foreach (int number in integerarray) { if (number != high && number != low) { sum += number; } } return sum; } //sum of numbers using high or low only if there is a duplicate of high or low static int sumSpecial(int[] integerArray) { var sum = sumWithoutHighAndLowScores(integerArray); var high = getHighestScore(integerArray); var low = getLowestScore(integerArray); var highs = 0; var lows = 0; foreach (int number in integerArray) { if (number == high) { highs++; } if (number == low) { lows++; } } if (lows > 1) { sum += low; } if (highs > 1) { sum += high; } return sum; }