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@@ -42,14 +42,14 @@ func indexOf(numbers []int, number int) int {
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func establishNewIndex(size int, current int, value int) int {
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delta := current + value
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if delta <= 0 {
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- delta = 0 - delta + 1
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+ delta = 0 - delta
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rest := delta % size
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return size - rest
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}
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if delta >= size {
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- return delta%size + 1
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+ return delta % size
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}
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return delta
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@@ -73,6 +73,7 @@ func addAt(numbers []int, value int, index int) []int {
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func mix(numbers []int) []int {
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size := len(numbers)
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+ edge := size - 1
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mixed := make([]int, size)
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copy(mixed, numbers)
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@@ -82,7 +83,7 @@ func mix(numbers []int) []int {
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}
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currentIndex := indexOf(mixed, numbers[i])
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- newIndex := establishNewIndex(size, currentIndex, numbers[i])
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+ newIndex := establishNewIndex(edge, currentIndex, numbers[i])
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mixed = removeAt(mixed, currentIndex)
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mixed = addAt(mixed, numbers[i], newIndex)
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@@ -97,8 +98,8 @@ func part1(mixed []int) int {
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size := len(mixed)
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for i := 1; i < 4; i++ {
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- newIndex := establishNewIndex(size, zeroIndex, i*1000)
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- result += mixed[newIndex-1]
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+ index := (zeroIndex + i*1000) % size
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+ result += mixed[index]
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}
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return result
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