How do I implement the minimum window substring in Swift?

To solve the Minimum Window Substring problem in Swift, we need to find the smallest substring of a given string that contains all the characters of another string. This problem can be approached using the sliding window technique, which helps maintain a window over the string while tracking the needed characters.

Keywords: Swift, Minimum Window Substring, Sliding Window, Algorithm, String Manipulation

Description: This example demonstrates how to implement the Minimum Window Substring algorithm in Swift, showcasing the use of a sliding window approach to efficiently find the desired substring.


        func minWindow(_ s: String, _ t: String) -> String {
            guard !s.isEmpty && !t.isEmpty else { return "" }

            var dictT = [Character: Int]()
            for char in t {
                dictT[char, default: 0] += 1
            }

            let required = dictT.count
            var left = 0, right = 0
            var formed = 0
            var windowCounts = [Character: Int]()
            var minLength = Int.max
            var minLeft = 0

            while right < s.count {
                let currentChar = Array(s)[right]
                windowCounts[currentChar, default: 0] += 1

                if let count = dictT[currentChar], windowCounts[currentChar] == count {
                    formed += 1
                }

                while left <= right && formed == required {
                    let charToCheck = Array(s)[left]

                    if right - left + 1 < minLength {
                        minLeft = left
                        minLength = right - left + 1
                    }

                    windowCounts[charToCheck, default: 0] -= 1
                    if let count = dictT[charToCheck], windowCounts[charToCheck] < count {
                        formed -= 1
                    }
                    left += 1
                }
                right += 1
            }
            return minLength == Int.max ? "" : String(Array(s)[minLeft..<(minLeft + minLength)])
        }

How do I implement the minimum window substring in Swift?

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How do I implement the minimum window substring in Swift?

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