first successful run to solve a simple puzzle

logic/strategies/strategy.go

@@ -12,8 +12,8 @@ import (
 
 type Strategy interface {
 	Init(f *board.Field)
-	ApplyAll() int
-	ApplyNext() bool
+	ApplyAll() []board.ExternalChange
+	ApplyNext() board.ExternalChange
 	Name() string
 	SearchProgressableCells() int
 }
@@ -40,23 +40,31 @@ func (b *Base) Init(f *board.Field) {
 	b.field = f
 }
 
-func (b *Base) ApplyAll() int {
+func (b *Base) ApplyAll() []board.ExternalChange {
+	changesCopy := make([]board.ExternalChange, len(b.changes))
+	copy(changesCopy, b.changes)
+
 	for _, change := range b.changes {
 		b.field.AddChange(&change)
 	}
-	len := len(b.changes)
+
 	b.changes = b.changes[:0]
 
-	return len
+	return changesCopy
 }
 
-func (b *Base) ApplyNext() bool {
+func (b *Base) ApplyNext() board.ExternalChange {
 	if len(b.changes) < 1 {
-		return false
+		return board.ExternalChange{}
 	}
+
+	changeCopy := b.changes[0]
+
 	b.field.AddChange(&b.changes[0])
+
 	b.changes = b.changes[1:]
-	return true
+
+	return changeCopy
 }
 
 func (b *Base) getName() string {