set a sequence on a list of items

Question

I need to set up a recursive function in C# to set the sequence number of a list of items. More specifically a bom. For each bom level, I need to start the sequence at 10, and increment of 10. How do I keep track of what level i'm at, and what counter to increment. This is driving me nuts.

Short example of data below, the real boms have thousands of lines and up to 12-15 levels.

Order	Level	Sequence
1	1	10
2	2	10
3	3	10
4	3	20
5	2	20
6	3	10
7	4	10
8	3	20
9	4	10
10	4	20
11	2	30
12	3	10
13	1	20
14	1	30

I indented the levels, to make the structure a bit more clear. And pasted the results of your answer to this. As you can see, the new levels are not sequenced properly.

Answer 1

I think i this case we can use the new language feature local function, and see if a recursive function is really necessary, as they are generally some of the hardest code to debug and maintain, only to be used sparingly, if at all this year, for any given year :)

    [Fact]
    public void SequencingRecursiveTest()
    {
        //  BOM like byte order mark in utf 8 text encoding? odd problem :D
        // Anyway we have a long list of values and want to emit the value with a sequence number, starting from 10 with increment 10
        // Like in most cases when contemplating recursion, first off  what about not using recursion to keep code maintainable and clean,
        // As it turns out, we can:

        //However super sneakily we have to reset all 'bom' sequence counts below the highest when an element in the sequence breaks the chain of same or greater

        var keyValues = new Dictionary<int, int>();
        var firstValue = 10;
        var increment = 10;
        int lastBom = 0;
        int greatesBom = 0;

        KeyValuePair<int, int> GetValueWithSequenceResetIfLowerThanLast(int bom)
        {
            bool reset = bom < lastBom;
            greatesBom = bom > greatesBom ? bom : greatesBom;

            if (reset)
            {
                foreach (int keyBom in keyValues.Keys)
                {
                    if (keyBom < greatesBom)
                        keyValues[keyBom] = firstValue;
                }
            }
            else if (keyValues.ContainsKey(bom))
            {
                keyValues[bom] = keyValues[bom] + increment;
            }
            else
            {
                keyValues.Add(bom, firstValue);
            }
            lastBom = bom;
            return new KeyValuePair<int, int>(bom, keyValues[bom]);
        }

        var valueList = new List<int> { 1, 2, 3, 3, 2, 3, 4, 3, 4, 4, 2, 3, 1, 1 };
        var valueSequenceList = valueList.Aggregate(
            new List<KeyValuePair<int, int>>(),
            (source, item) =>
            {
                source.Add(GetValueWithSequenceResetIfLowerThanLast(item));
                return source;
            }
        );

        foreach (var element in valueSequenceList)
            System.Diagnostics.Debug.WriteLine($"{element.Key}: {element.Value}");

    }