Implement KMPMatch and KMPSearch function to check if pattern exists and the index of matched pattern

KMP.swift

import Foundation

func computeLPS(_ pattern: String) -> [Int] {
    let array = Array(pattern).map{String($0)}
    var i = 1
    var j = 0
    var lps = Array(repeating: 0, count: array.count)
    
    while i < array.count {
        if array[j] == array[i] {
            j += 1
            lps[i] = j
            i += 1
        }
        else {
            if j != 0 {
                j = lps[j - 1]
            }
            else {
                i += 1
            }
        }
    }
    
    return lps
}

func KMPMatch(_ str_: String, _ pattern_: String) -> Bool {
    let lps = computeLPS(pattern_)
    let str = Array(str_).map{ String($0) }
    let pattern = Array(pattern_).map{ String($0) }
    
    var i = 0
    var j = 0
    var contains = false
    
    while i < str.count {
        if str[i] == pattern[j] {
            i += 1
            j += 1
        }
        
        if j == pattern.count {
            contains = true
            j = 0
        }
        
        if i < str.count && str[i] != pattern[j] {
            if j != 0 {
                j = lps[j - 1]
            }
            else {
                i += 1
            }
        }
    }
    
    return contains
}

func KMPSearch(_ str_: String, _ pattern_: String) -> [Int] {
    let lps = computeLPS(pattern_)
    let str = Array(str_).map{ String($0) }
    let pattern = Array(pattern_).map{ String($0) }
    
    var i = 0
    var j = 0
    var result = [Int]()
    
    while i < str.count {
        if str[i] == pattern[j] {
            i += 1
            j += 1
        }
        
        if j == pattern.count {
            result.append(i - j)
            j = 0
        }
        
        if i < str.count && str[i] != pattern[j] {
            if j != 0 {
                j = lps[j - 1]
            }
            else {
                i += 1
            }
        }
    }
    
    return result
}