43 lines
853 B
Go
43 lines
853 B
Go
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// Functions for operating on polymers from day 5.
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package polymer
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import (
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"bytes"
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)
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func ApplyReactions(data []byte) string {
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result := data
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changed := true
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for changed {
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result, changed = React(result)
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}
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return string(result)
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}
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// React finds substrings of the form "xX" or "Xx" and removes them, returning
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// the resulting bytes.
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func React(data []byte) ([]byte, bool) {
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result := bytes.Buffer{}
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changed := false
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for i := 0; i < len(data); i++ {
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if i < len(data)-1 &&
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data[i] != data[i+1] &&
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string(bytes.ToLower([]byte{data[i]})) == string(bytes.ToLower([]byte{data[i+1]})) {
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// we've found a reduction; skip over it without writing
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// return append(data[:i], data[i+2:]...), true
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i++
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changed = true
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continue
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}
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result.WriteByte(data[i])
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}
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// No changes possible.
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return result.Bytes(), changed
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}
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