Merge pull request neetcode-gh#2155 from AyselHeydarova/leetcode-0076

Create: 0076-minimum-window-substring.swift

0076-minimum-window-substring.swift

@@ -0,0 +1,51 @@
+class Solution {
+ func minWindow(_ s: String, _ t: String) -> String {
+ if t.isEmpty { return "" }
+
+ var countT: [Character : Int] = [:]
+ var window: [Character : Int] = [:]
+ let stringArray = Array(s)
+
+ // Storing each char and its count in hashMap
+ for char in t {
+ countT[char, default: 0] += 1
+ }
+
+ var have = 0
+ let need = t.count
+ var resultRange = (-1, -1)
+ var resultLength = Int.max
+ var l = 0
+
+ for r in 0...s.count - 1 {
+ let char = stringArray[r]
+ window[char, default: 0] += 1
+
+ if countT.contains(where: { $0.key == char }) && window[char] == countT[char] {
+ // for the case of repeated characters "have" should be increased by count, not by 1
+ have += countT[char, default: 0]
+ }
+
+ while have == need {
+ // update result
+ if r - l + 1 < resultLength {
+ resultRange = (l, r)
+ resultLength = r - l + 1
+ }
+ // pop from left of the window
+ window[stringArray[l], default: 0] -= 1
+
+ if countT.contains(where: { $0.key == stringArray[l] })
+ && window[stringArray[l], default: 0] < countT[stringArray[l], default: 0] {
+ //subtract all count, because in second iteration will be added total count of char.
+ have -= countT[stringArray[l], default: 0]
+ }
+
+ l += 1
+ }
+ }
+
+ guard resultLength != Int.max else { return "" }
+ return String(stringArray[resultRange.0...resultRange.1])
+ }
+}