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main.go
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main.go
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package main
import (
"fmt"
"unicode/utf8"
)
// check that string has one step changes
// or one insert or one remove or one replace
// utf-8 strings
func main() {
// one replace
str1 := "qwerty日の出asdf"
str2 := "qwerty日のgasdf"
fmt.Println(isOneEditAway(str1, str2))
fmt.Println(isOneEditAwayV2(str1, str2))
fmt.Println("")
// one insert
str1 = "qwerty日の出asdf"
str2 = "qwerty日の出asdf1"
fmt.Println(isOneEditAway(str1, str2))
fmt.Println(isOneEditAwayV2(str1, str2))
fmt.Println("")
// two insert
str1 = "qwerty日の出asdf"
str2 = "qwerty日の出asdf12"
fmt.Println(isOneEditAway(str1, str2))
fmt.Println(isOneEditAwayV2(str1, str2))
fmt.Println("")
// one remove
str1 = "qwerty日の出asdf"
str2 = "qwerty日の出asd"
fmt.Println(isOneEditAway(str1, str2))
fmt.Println(isOneEditAwayV2(str1, str2))
fmt.Println("")
// two remove
str1 = "qwerty日の出asdf"
str2 = "qwerty日の出as"
fmt.Println(isOneEditAway(str1, str2))
fmt.Println(isOneEditAwayV2(str1, str2))
fmt.Println("")
}
// cpu - O(N), where N - len(s1)+len(s2), we find len by iterating each string
// for ASCII we can get cpu - O(N), where N - shortest of string, if get length as length of bytes (not rune)
// memp - O(1), we do not allocate new spaces
//
// replace do not change lenght of strigns
// one insert or one remove change length for one char
func isOneEditAway(s1, s2 string) bool {
if utf8.RuneCountInString(s1) == utf8.RuneCountInString(s2) {
return isOneEditReplace(s1, s2)
} else if utf8.RuneCountInString(s1)+1 == utf8.RuneCountInString(s2) {
return isOneEditInsertFirstStr(s1, s2)
} else if utf8.RuneCountInString(s1) == utf8.RuneCountInString(s2)+1 {
return isOneEditInsertFirstStr(s2, s1)
}
return false
}
// we not compare byte by byte
// we compare rune by rune
func isOneEditReplace(s1, s2 string) bool {
// flag for detect first diff
isDiff := false
idx1 := 0
idx2 := 0
for idx1 < len(s1) && idx2 < len(s2) {
r, len := utf8.DecodeRuneInString(s1[idx1:])
// if not utf8 return false
if r == utf8.RuneError {
return false
}
r2, len2 := utf8.DecodeRuneInString(s2[idx2:])
// if not utf8 return false
if r2 == utf8.RuneError {
return false
}
if len != len2 || r != r2 {
// we get second diff char
if isDiff {
return false
}
isDiff = true
}
idx1 += len
idx2 += len2
}
return true
}
func isOneEditInsertFirstStr(s1, s2 string) bool {
idx1 := 0
idx2 := 0
for idx1 < len(s1) && idx2 < len(s2) {
r, len := utf8.DecodeRuneInString(s1[idx1:])
// if not utf8 return false
if r == utf8.RuneError {
return false
}
r2, len2 := utf8.DecodeRuneInString(s2[idx2:])
// if not utf8 return false
if r2 == utf8.RuneError {
return false
}
if len != len2 || r != r2 {
if idx1 != idx2 {
return false
}
idx2 += len2
} else {
idx1 += len
idx2 += len2
}
}
return true
}
// version 2 (less code, less clear)
func isOneEditAwayV2(s1, s2 string) bool {
s1len := utf8.RuneCountInString(s1)
s2len := utf8.RuneCountInString(s2)
diffLen := (s1len - s2len)
if diffLen < 0 {
diffLen *= -1
}
if diffLen > 1 {
return false
}
if s1len > s2len {
// copy string in Go do not copy underlying array just string header (pointer to array and len)
// so it's cheap
s1, s2 = s2, s1
}
// flag for detect first diff
isDiff := false
idx1 := 0
idx2 := 0
for idx1 < len(s1) && idx2 < len(s2) {
r, len := utf8.DecodeRuneInString(s1[idx1:])
// if not utf8 return false
if r == utf8.RuneError {
return false
}
r2, len2 := utf8.DecodeRuneInString(s2[idx2:])
// if not utf8 return false
if r2 == utf8.RuneError {
return false
}
if len != len2 || r != r2 {
// we get second diff char
if isDiff {
return false
}
isDiff = true
if s1len == s2len {
idx1 += len
}
} else {
idx1 += len
}
idx2 += len2
}
return true
}