using System;
using System.Collections.Generic;
using System.Linq;
static class Program
{
public static void Main(string[] args)
{
var list1 = new int?[] { 1, 2, 3, 4, 5 };
var list2 = new int?[] { 3, 4, 5, 6, 7 };
var list3 = new int?[] { 6, 9, 9 };
var lockstep = LockStepSequences(new[] { list1, list2, list3 });
foreach (var step in lockstep)
Console.WriteLine(string.Join("\t", step.Select(i => i.HasValue ? i.Value.ToString() : "null").ToArray()));
}
public static IEnumerable<IEnumerable<T>> LockStepSequences<T>(this IEnumerable<IEnumerable<T>> sequences)
{
var iters = sequences
.Select((s, index) => new { active=true, index, enumerator = s.GetEnumerator() })
.ToArray();
var isActive = iters.Select(it => it.enumerator.MoveNext()).ToArray();
var numactive = isActive.Count(flag => flag);
try
{
while (numactive > 0)
{
T min = iters
.Where(it => isActive[it.index])
.Min(it => it.enumerator.Current);
var row = new T[iters.Count()];
for (int j = 0; j < isActive.Length; j++)
{
if (!isActive[j] || !Equals(iters[j].enumerator.Current, min))
continue;
row[j] = min;
if (!iters[j].enumerator.MoveNext())
{
isActive[j] = false;
numactive -= 1;
}
}
yield return row;
}
}
finally
{
foreach (var iter in iters) iter.enumerator.Dispose();
}
}
}
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