[LeetCode] Longest Substring Without Repeating Characters

https://leetcode.com/problems/longest-substring-without-repeating-characters/

description：

Given a string, find the length of the longest substring without repeating characters.

Example 1:

Input: "abcabcbb"
Output: 3 
Explanation: The answer is"abc", with the length of 3. 

Example 2:

Input: "bbbbb"
Output: 1
Explanation: The answer is"b", with the length of 1.

Example 3:

Input: "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring.

---

• 方案一

func lengthOfLongestSubstring(s string) int {
    var lastLongestLen, curLen int
    bytes := []byte(s)
    subStr := ""
    for i, byte := range bytes {
        if index := strings.Index(subStr, string(byte)); -1 != index {
            curLen = len(subStr)
            if curLen > lastLongestLen {
                lastLongestLen = curLen
            }
            subStr = subStr[index+1:]
            curLen = len(subStr)
        }
        subStr = subStr + string(bytes[i])
        curLen++
    }
    if curLen > lastLongestLen {
        return curLen
    } 
    return lastLongestLen
}

• 方案二：

直接使用bytes試試，內存使用量下降了

func lengthOfLongestSubstring(s string) int {
    var lastLongestLen, curLen int
    bytes := []byte(s)
    subBytes := []byte{}
    for _, b := range bytes {
        if index := indexOfEle(subBytes, b); -1 != index {
            if curLen > lastLongestLen {
                lastLongestLen = curLen
            }
            subBytes = subBytes[index+1:]
            curLen = curLen - index - 1
        }
        subBytes = append(subBytes, b)
        curLen++
    }
    if curLen > lastLongestLen {
        return curLen
    }
    return lastLongestLen
}

func indexOfEle(in []byte, ele byte) int {
    for i, b := range in {
        if ele == b {
            return i
        }
    }
    return -1
}