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Run-length encoding: Difference between revisions
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Line 3,712:
- decode [(#"a",5),(#"h",6),(#"m",7),(#"u",1),(#"i",7),(#"a",6)];
val it = "aaaaahhhhhhmmmmmmmuiiiiiiiaaaaaa" : string
</pre>
=={{header|Swift}}==
Using array as internal representation of encoded input:
<lang swift>import Foundation
// "WWWBWW" -> [(3, W), (1, B), (2, W)]
func encode(input: String) -> [(Int, Character)] {
return input.characters.reduce([(Int, Character)]()) {
if $0.last?.1 == $1 { var r = $0; r[r.count - 1].0++; return r }
return $0 + [(1, $1)]
}
}
// [(3, W), (1, B), (2, W)] -> "WWWBWW"
func decode(encoded: [(Int, Character)]) -> String {
return encoded.reduce("") { $0 + String(count: $1.0, repeatedValue: $1.1) }
}
</lang>
'''Usage:'''
<lang swift>
let input = "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW"
let output = decode(encode(input))
print(output == input)
</lang>
{{Out}}
<pre>true</pre>
Converting encoded array into the string and then decoding it using NSScanner:
<lang swift>// "3W1B2W" -> "WWWBWW"
func decode(encoded: String) -> String {
let scanner = NSScanner(string: encoded)
var char: NSString? = nil
var count: Int = 0
var out = ""
while scanner.scanInteger(&count) {
while scanner.scanCharactersFromSet(NSCharacterSet.letterCharacterSet(), intoString: &char) {
out += String(count: count, repeatedValue: Character(char as! String))
}
}
return out
}
</lang>
<lang swift>let encodedString = encode(input).reduce("") { $0 + "\($1.0)\($1.1)" }
print(encodedString)
let outputString = decode(encodedString)
print(outputString == input)
</lang>
{{Out}}
<pre>
12W1B12W3B24W1B14W
true
</pre>
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