static ISorterStage MutateSorterStageOdd(this IRando rando, ISorterStage sorterStage)
{
var map = sorterStage.GetMap();
var fv = map.FixedValue();
var rems = map.Select(i => true).ToArray();
rems[fv] = false;
var lv = rando.SelectFromRemaining(map, rems);
var hv = sorterStage[lv];
map[lv] = fv;
map[fv] = lv;
map[hv] = hv;
return(new SorterStage(
order: sorterStage.Order,
terms: map,
stageNumber: sorterStage.StageNumber));
}
static ISorterStage MutateSorterStageEven(this IRando rando, ISorterStage sorterStage)
{
var map = sorterStage.GetMap();
var rems = map.Select(i => true).ToArray();
var aX = rando.SelectFromRemaining(map, rems);
var aY = map[aX];
rems[aY] = false;
var bX = rando.SelectFromRemaining(map, rems);
var bY = map[bX];
rems[bY] = false;
map[aX] = bY;
map[aY] = bX;
map[bX] = aY;
map[bY] = aX;
return(new SorterStage(
order: sorterStage.Order,
terms: map,
stageNumber: sorterStage.StageNumber));
}
