"3. Longest Substring Without Repeating Characters" accepted solution

3-longest-substr-no-repeat-chars.go

@@ -0,0 +1,91 @@
+package main
+
+func lengthOfLongestSubstringBruteforce(s string) int {
+	//max chars = 0
+	//loop l starts from max length and decreasing by 1
+	//loop i starts from 0 and goes until i <= max length - l increasing i by 1 each iteration
+	//char counter set to 0 before j loop
+	//char map is set to empty before j loop, map space is reserved for 50000 characters
+	//loop j starts from i and goes until j < i + l, increasing j by 1 on each iteration
+	//on each step we add character to map and we increase char counter
+	//then we check if len(map) == char counter, if they are not equal we break the j loop
+	//but if they are equal then we check if char counter is bigger than max chars and if it is, assign new max value
+
+	maxChars := 0
+	for l := len(s); l >= 0; l-- {
+		for i := 0; i <= len(s)-l; i++ {
+			charCounter := 0
+			charMap := make(map[uint8]interface{}, 50000)
+
+			for j := i; j < i+l; j++ {
+				charMap[s[j]] = nil
+				charCounter++
+				if len(charMap) != charCounter {
+					break
+				}
+				if maxChars < charCounter {
+					maxChars = charCounter
+				}
+			}
+		}
+	}
+	return maxChars
+}
+
+func lengthOfLongestSubstringSlidingWindow(s string) int {
+	maxChars := 1
+
+	if len(s) == 0 {
+		return 0
+	}
+
+	for wndSz := 2; wndSz <= len(s); wndSz++ {
+		charMap := [255]int{}
+		charMapSize := 0
+
+		repeat := false
+		for wndPos := 0; wndPos < wndSz; wndPos++ {
+			charMap[s[wndPos]]++
+			if charMap[s[wndPos]] > 1 {
+				repeat = true
+			} else {
+				charMapSize++
+			}
+		}
+
+		if !repeat && (charMapSize == wndSz) && (maxChars < wndSz) {
+			maxChars = wndSz
+		}
+
+		for wndPos := 1; wndPos <= len(s)-wndSz; wndPos++ {
+			repeat = true
+
+			charMap[s[wndPos-1]]--
+			if charMap[s[wndPos-1]] == 1 {
+				repeat = false
+			}
+
+			if charMap[s[wndPos-1]] <= 0 {
+				charMap[s[wndPos-1]] = 0
+				charMapSize--
+			}
+
+			charMap[s[wndPos+wndSz-1]]++
+			if charMap[s[wndPos+wndSz-1]] > 1 {
+				repeat = true
+			} else {
+				charMapSize++
+			}
+
+			if !repeat && (charMapSize == wndSz) && (maxChars < wndSz) {
+				maxChars = wndSz
+			}
+		}
+	}
+
+	return maxChars
+}
+
+func LengthOfLongestSubstring(s string) int {
+	return lengthOfLongestSubstringSlidingWindow(s)
+}