Stream merge: Difference between revisions
Added Kotlin
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(Added Kotlin) |
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<pre>1245781011
123456789101112</pre>
=={{header|Kotlin}}==
Uses the same data as the REXX entry. As Kotlin lacks a Heap class, when merging N files, we use a nullable MutableList instead. All comparisons are text based even when the files contain nothing but numbers.
<lang scala>// version 1.2.21
import java.io.File
fun merge2(inputFile1: String, inputFile2: String, outputFile: String) {
val file1 = File(inputFile1)
val file2 = File(inputFile2)
require(file1.exists() && file2.exists()) { "Both input files must exist" }
val reader1 = file1.bufferedReader()
val reader2 = file2.bufferedReader()
val writer = File(outputFile).printWriter()
var line1 = reader1.readLine()
var line2 = reader2.readLine()
while (line1 != null && line2 != null) {
if (line1 <= line2) {
writer.println(line1)
line1 = reader1.readLine()
}
else {
writer.println(line2)
line2 = reader2.readLine()
}
}
while (line1 != null) {
writer.println(line1)
line1 = reader1.readLine()
}
while (line2 != null) {
writer.println(line2)
line2 = reader2.readLine()
}
reader1.close()
reader2.close()
writer.close()
}
fun mergeN(inputFiles: List<String>, outputFile: String) {
val files = inputFiles.map { File(it) }
require(files.all { it.exists() }) { "All input files must exist" }
val readers = files.map { it.bufferedReader() }
val writer = File(outputFile).printWriter()
var lines = readers.map { it.readLine() }.toMutableList()
while (lines.any { it != null }) {
val line = lines.filterNotNull().min()
val index = lines.indexOf(line)
writer.println(line)
lines[index] = readers[index].readLine()
}
readers.forEach { it.close() }
writer.close()
}
fun main(args:Array<String>) {
val files = listOf("merge1.txt", "merge2.txt", "merge3.txt", "merge4.txt")
merge2(files[0], files[1], "merged2.txt")
mergeN(files, "mergedN.txt")
// check it worked
println(File("merged2.txt").readText())
println(File("mergedN.txt").readText())
}</lang>
{{out}}
<pre>
1
17
19
33
500
8
1
17
19
1999
2999
2e3
3000
33
3999
500
8
</pre>
=={{header|Perl}}==
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