LeetCode: Longest Substring Without Repeating Characters

Posted on January 26, 2018July 26, 2020 by braindenny

Longest Substring Without Repeating Characters

Similar Problems:

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

Examples:

Given “abcabcbb”, the answer is “abc”, which the length is 3.

Given “bbbbb”, the answer is “b”, with the length of 1.

Given “pwwkew”, 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.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

// https://code.dennyzhang.com/longest-substring-without-repeating-characters
// Basic Ideas: Sliding window
//
// Complexity: Time O(n), Space O(1)
func lengthOfLongestSubstring(s string) int {
    l := make([]int, 128)
    res := 0
    // s[i...j]
    i := 0
    for j, v := range s {
        index := byte(v)
        l[index]++
        for l[index] > 1 {
            l[s[i]]--
            i++
        }
        if j-i+1 > res {
            res = j-i+1
        }
    }
    return res
}

// https://code.dennyzhang.com/longest-substring-without-repeating-characters
// Basic Ideas: Sliding window
//
// Complexity: Time O(n), Space O(n)
func lengthOfLongestSubstring(s string) int {
    m := map[byte]int{}
    res := 0
    // s[i...j]
    i := 0
    for j, _ := range s {
        v := byte(s[j])
        m[v]++
        for m[v]>1 {
            m[s[i]]--
            i++
        }
        if j-i+1 > res {
            res = j-i+1
        }
    }
    return res
}

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