Question

How to remove the last n occurrences of a substring in a string in Swift

Answer 1

import Foundation

// Remove last n occurrences of a substring
func removeLastNOccurrences(_ s: String, sub: String, n: Int) -> String {
    var positions: [String.Index] = []
    var searchStart = s.startIndex

    // Find all occurrences
    while let range = s.range(of: sub, range: searchStart..<s.endIndex) {
        positions.append(range.lowerBound)
        searchStart = range.upperBound
    }

    // Remove from the end
    var result = s
    var remaining = n

    for pos in positions.reversed() {
        if remaining == 0 { break }
        let end = result.index(pos, offsetBy: sub.count)
        result.removeSubrange(pos..<end)
        remaining -= 1
    }

    return result
}

// Remove extra spaces (collapse multiple spaces, trim ends)
func removeExtraSpaces(_ s: String) -> String {
    s.split(whereSeparator: { $0.isWhitespace })
     .joined(separator: " ")
}

let text = "abc xyz xyz abc xyzabcxyz abc"

let result = removeLastNOccurrences(text, sub: "xyz", n: 3)
print(result)

let cleaned = removeExtraSpaces(result)
print(cleaned)



/*
run:

abc xyz  abc abc abc
abc xyz abc abc abc

*/

 

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