438. Find All Anagrams in a String

find-all-anagrams-in-a-string.go

// https://leetcode.com/problems/find-all-anagrams-in-a-string/
//
// Time: O(n)
// Space: O(1)
//
// n - number of elements in array

// .................... //

func findAnagrams(s string, p string) []int {
    n := len(s)
    m := len(p)
    if n < m {
        return nil
    }

    target := [26]int{}
    for i := range m {
        idx := p[i] - 'a'
        target[idx]++
    }

    key := [26]int{}
    res := make([]int, 0)

    for i := range m {
        idx := s[i] - 'a'
        key[idx]++
    }
    if key == target {
        res = append(res, 0)
    }

    l, r := 0, m
    for r < n {
        key[s[l]-'a']--
        key[s[r]-'a']++

        l++
        r++

        if key == target {
            res = append(res, l)
        }
    }

    return res
}