RosettaCodeData/Task/Longest-common-substring/PowerShell/longest-common-substring.psh

63 lines
1.5 KiB
Plaintext

function lcs([String]$a, [String]$b)
{
if ([String]::IsNullOrEmpty($a) -or [String]::IsNullOrEmpty($b))
{
return ""
}
$startIndex, $size = -1, -1
for ($k = 0; $k -lt $a.Length; ++$k)
{
for ($i, $j, $d = $k, 0, 0; ($i -lt $a.Length) -and ($j -lt $b.Length); ++$i, ++$j)
{
if ($a.Chars($i) -eq $b.Chars($j))
{
$d += 1
if ($size -lt $d)
{
$startIndex = $i - $d + 1
$size = $d
}
}
else
{
$d = 0
}
}
}
for ($k = 1; $k -lt $b.Length; ++$k)
{
for ($i, $j, $d = 0, $k, 0; ($i -lt $a.Length) -and ($j -lt $b.Length); ++$i, ++$j)
{
if ($a.Chars($i) -eq $b.Chars($j))
{
$d += 1
if ($size -lt $d)
{
$startIndex = $i - $d + 1
$size = $d
}
}
else
{
$d = 0
}
}
}
if ($size -lt 0)
{
return ""
}
return $a.Substring($startIndex, $size)
}
function Print-Lcs([String]$a, [String]$b)
{
return "lcs $a $b = $(lcs $a $b)"
}
Print-Lcs 'thisisatest' 'testing123testing'
Print-Lcs 'testing' 'sting'
Print-Lcs 'thisisatest_stinger' 'testing123testingthing'
Print-Lcs 'thisisatest_stinger' 'thisis'
Print-Lcs 'testing123testingthing' 'thisis'
Print-Lcs 'thisisatest' 'thisisatest'