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https://github.com/kovidgoyal/kitty
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5d1215b11d
- Declares --prefix-free CLI flag in main.py. - Implements dynamic index offset shifting in marks.go to prevent generating hints that prefix other hints. - Integrates prefix-free encoding in main.go. - Includes tests. Implements #10195
63 lines
1.6 KiB
Go
63 lines
1.6 KiB
Go
// License: GPLv3 Copyright: 2026, Kovid Goyal, <kovid at kovidgoyal.net>
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package hints
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// hints_to_skip calculates how many hints to skip based on the given n and
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// alphabet size so that the next n hints generated by expanding the prefix tree
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// of an alphabet of size alphabetSize will be prefix-free.
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//
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// The result is 1-based, meaning that the first hint to be skipped is the first
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// non-empty hint.
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//
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// For example, if alphabet was "abc" and n was 5, the first non-empty hints
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// from that alphabet would be: "a", "b", "c", "aa", "ab", "ac", ...
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// the result of hints_to_skip would be 1, and this would mean that if you skip
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// "a" from the list above, the next 5 hints are prefix-free:
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// "b", "c", "aa", "ab", "ac".
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//
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// See issue #10195 for an informal proof on why this function works.
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func hints_to_skip(n int, alphabetSize int) int {
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if n < 2 {
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n = 2
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}
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return (n - 2) / (alphabetSize - 1)
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}
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// generate_prefix_free_hint generates the hint corresponding to the given index
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// in the breadth-first traversal of the prefix tree generated by the given
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// alphabet.
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//
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// For example, given the alphabet "abc", the hints would be generated in
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// the following order:
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// 1. "a"
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// 2. "b"
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// 3. "c"
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// 4. "aa"
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// 5. "ab"
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// 6. "ac"
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// 7. "ba"
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// 8. "bb"
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// 9. "bc"
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// 10. "ca"
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// 11. "cb"
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// 12. "cc"
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// 13. "aaa"
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// ...
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//
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// Indices are 1-based on non-empty hints; index=0 returns an empty (invalid)
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// hint.
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func generate_prefix_free_hint(index int, alphabet string) string {
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l := len(alphabet)
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hint := ""
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index -= 1
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for index >= 0 {
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mod := index % l
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char := string(alphabet[mod])
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index /= l
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hint = char + hint
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index -= 1
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}
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return hint
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}
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