c# refactoring with linq query

Question

I am trying to improve my linq syntax coding and i was wondering if anyone could show me a better way of writing this code below.Question is taken from leetcode https://leetcode.com/problems/kids-with-the-greatest-number-of-candies/. Thanks

        public static IList<bool> KidsWithCandies(int[] candles, int extraCandies)
        {
           var kidCandle = candles.Select(x => x+ extraCandies);
           var con = new List<bool>();
            foreach(var kid in kidCandle)
            {
                if (kid >= candles.Max())
                    con.Add(true);
                else
                    con.Add(false);
            }

           return con;
        }

https://leetcode.com/problems/kids-with-the-greatest-number-of-candies/

int max = candles.Max(); List<bool> con = candles.Select(x => x + extraCandies>= max).ToList(); — Mohammed Sajid
– Mohammed Sajid, Commented May 29, 2020 at 16:30

Ehsan Sajjad · Accepted Answer · 2020-05-29 16:42:08Z

3

Linq also does looping but just a syntacitc sugar, but we can write a Select for the foreach. So the code :

var con = new List<bool>();
foreach(var kid in kidCandle)
{
    if (kid >= candles.Max())
        con.Add(true);
    else
        con.Add(false);
}

can be replaced with:

public static IList<bool> KidsWithCandies(int[] candles, int extraCandies)
{
   var kidCandle = candles.Select(x => x+ extraCandies);
   var maxCandles = candles.Max();
   var con = kidCandle.Select(kid => (kid >= maxCandles)).ToList();
   return con;
}

even the whole method could be written like:

public static IList<bool> KidsWithCandies(int[] candles, int extraCandies)
{
    var maxCandles = candles.Max();
    return candles.Select(x => x+ extraCandies)
                 .Select(kid => (kid >= maxCandles)).ToList();
}

Now more simpler:

public static IList<bool> KidsWithCandies(int[] candles, int extraCandies)
{
   var maxCandles = candles.Max();
   var con = candles.Select(kid => (kid + extraCandies >= maxCandles)).ToList();
   return con;
}

we can even avoid var :

 public static IList<bool> KidsWithCandies(int[] candles, int extraCandies)
 {
     var maxCandles = candles.Max();     
     return candles.Select(kid => (kid + extraCandies >= maxCandles)).ToList();
 }

edited May 29, 2020 at 16:42

answered May 29, 2020 at 16:24

Ehsan Sajjad

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3 Comments

itsme86 Over a year ago

You don't need to ? true : false something that's already a boolean. It's kind of like doing bool foo = true ? true : false;

Christoph Lütjen Over a year ago

Or

public static IList<bool> KidsWithCandies(int[] candles, int extraCandies) => candles.Select(kid => (kid + extraCandies >= candles.Max()));

Yurii N. Over a year ago

Current query has complexity O(n^2), due to calculating Max in every Select call. It is strongly advised to move Max calculation to dedicated variable.

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