Longest common substring: Difference between revisions

=={{header|Swift}}==

<lang swift>func lComSubStr<

S0: Sliceable, S1: Sliceable, T: Equatable where

S0.Generator.Element == T, S1.Generator.Element == T,

S0.Index.Distance == Int, S1.Index.Distance == Int

>(w1: S0, _ w2: S1) -> S0.SubSlice {

var (len, end) = (0, 0)

let empty = Array(Repeat(count: w2.count + 1, repeatedValue: 0))

var mat: [[Int]] = Array(Repeat(count: w1.count + 1, repeatedValue: empty))

for (i, sLett) in w1.enumerate() {

for (j, tLett) in w2.enumerate() where tLett == sLett {

let curLen = mat[i][j] + 1

mat[i + 1][j + 1] = curLen

if curLen > len {

len = curLen

end = i

}

}

}

return w1[advance(w1.startIndex, (end + 1) - len)...advance(w1.startIndex, end)]

}

func lComSubStr(w1: String, _ w2: String) -> String {

return String(lComSubStr(w1.characters, w2.characters))

}</lang>

Output:

<lang swift>lComSubStr("thisisatest", "testing123testing") // "test"</lang>