60 lines
950 B
Go
60 lines
950 B
Go
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package qrcode
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// kmp is variant of kmp algorithm to count the pattern been in
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// src slice.
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// DONE(@yeqown): implement this in generic way.
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func kmp[v comparable](src, pattern []v, next []int) (count int) {
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if next == nil {
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next = kmpGetNext(pattern)
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}
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slen := len(src)
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plen := len(pattern)
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i := 0 // cursor of src
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j := 0 // cursor of pattern
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loop:
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for i < slen && j < plen {
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if j == -1 || src[i] == pattern[j] {
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i++
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j++
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} else {
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j = next[j]
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}
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}
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if j == plen {
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if i-j >= 0 {
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count++
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}
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// reset cursor to count duplicate pattern.
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// such as: "aaaa" and "aa", we want 3 rather than 2.
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i -= plen - 1
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j = 0
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goto loop
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}
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return count
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}
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func kmpGetNext[v comparable](pattern []v) []int {
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fail := make([]int, len(pattern))
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fail[0] = -1
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j := 0
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k := -1
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for j < len(pattern)-1 {
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if k == -1 || pattern[j] == pattern[k] {
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k++
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j++
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fail[j] = k
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} else {
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k = fail[k]
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}
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}
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return fail
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}
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