Improve day 20

day20/common/mixing.go

@@ -13,42 +13,24 @@ type Arrangement struct {
 
 func (arrangement *Arrangement) Mix(number int) {
   newSequence := make([]int, len(arrangement.numbers))
-  oldIndices := make([]int, 0, len(arrangement.numbers))
   var newIndex int
 
+  currentIndices := make([]int, len(arrangement.numbers))
   for i := range arrangement.numbers {
-    oldIndices = append(oldIndices, i)
+    currentIndices[i] = i
     newSequence[i] = arrangement.numbers[i]
   }
 
   for i := 0; i < number; i++ {
-    currentIndices := make([]int, len(oldIndices))
-    for j := range oldIndices {
-      currentIndices[j] = oldIndices[j]
-    }
-
-    for j := 0; j < len(oldIndices); j++ {
+    for j := 0; j < len(currentIndices); j++ {
       offset := currentIndices[j]
       currentNumber := arrangement.numbers[j]
       newIndex = offset + currentNumber
       newIndex = (newIndex % (len(newSequence) - 1) + len(newSequence) - 1) % (len(newSequence) - 1)
 
-      if offset == 0 {
-        newSequence = newSequence[1:]
-      } else if offset == len(newSequence) - 1 {
-        newSequence = newSequence[:len(newSequence) - 1]
-      } else {
       newSequence = append(newSequence[:offset], newSequence[offset + 1:]...)
-      }
-
-      if newIndex == 0 {
-        newSequence = append([]int{currentNumber}, newSequence...)
-      } else if newIndex == len(newSequence) {
-        newSequence = append(newSequence, currentNumber)
-      } else {
       newSequence = append(newSequence[:newIndex+1], newSequence[newIndex:]...)
       newSequence[newIndex] = currentNumber
-      }
 
       for i := range currentIndices {
         if newIndex <= currentIndices[i] && currentIndices[i] < offset {
@@ -58,12 +40,6 @@ func (arrangement *Arrangement) Mix(number int) {
         }
       }
       currentIndices[j] = newIndex
-
-      offset %= len(newSequence)
-    }
-
-    for i := range currentIndices {
-      oldIndices[i] = currentIndices[i]
     }
   }