How Can I Efficiently Find All Overlapping Pattern Matches in Go?

Overlapping Pattern Matching in Golang: A Comprehensive Guide

Matching overlapping patterns can pose a challenge in Go, given the limitations of the regexp package. This article delves into an alternative approach that utilizes the simplicity and efficiency of strings.Index to effectively achieve overlapping pattern matching.

The Problem:

Given a string and a pattern, such as "..#..", we aim to find all instances of the pattern irrespective of their overlap. The existing regexp.FindAllStringSubmatchIndex method only captures non-overlapping matches.

The Solution:

Instead of relying on regexp, we construct a custom solution using strings.Index and a for loop:

func FindOverlappingPattern(input, pattern string) []int {
    idx := []int{}
    j := 0
    for {
        i := strings.Index(input[j:], pattern)
        if i == -1 {
            break
        }
        fmt.Println(j)
        idx = append(idx, j+i)
        j += i + len(pattern)
    }
    fmt.Println("Indexes:", idx)
    return idx
}

Explanation:

This function iteratively searches for the pattern using strings.Index within the remaining part of the input string. Each positive index found is added to the list of indexes. The loop continues until no further matches are found.

Sample Usage:

input := "...#...#....#.....#..#..#..#......."
pattern := "..#.."
result := FindOverlappingPattern(input, pattern)
// result: [1, 10, 16, 22, 29]

Benefits:

This approach is straightforward and leverages the native string searching capabilities of Go. It outperforms regex-based solutions in both simplicity and efficiency for simple pattern matching tasks.

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