[Leetcode X Golang] Study Note 03

3. Longest Substring Without Repeating Characters

Code:

import "math"
func lengthOfLongestSubstring(s string) int {
    window := make(map[byte]bool)
    var l, i, j, r int
    l = len(s)
    
    for i < l && j < l {
        if _, ok := window[s[j]]; ok {
            delete(window, s[i])
            i++
        } else {
            window[s[j]] = true
            j++
            r = int(math.Max(float64(r), float64(j - i)))
        }
    }
    return r
}

Code Optimized:

import "math"
func lengthOfLongestSubstring(s string) int {
    var charset [128]int
    i := 0
    r := 0
    for j, ch := range s {
        i = int(math.Max(float64(charset[ch]), float64(i)))
        r = int(math.Max(float64(r), float64(j - i + 1)))
        charset[ch] = j + 1
    }
    return r
}

Notes:

• golang has no set type since no generics in go
• to delete key in golang, use delete(map, key)
• there is no max function for int, have to convert to float64 first
• when loop thru string, each char is byte type, and it's magically assignable to int array.