codewars/go/kyu7/find_n_1_common_letters/k.go

package kata

import (
	"fmt"
	"sort"
	"strings"
)

func uniqueStrings(sl []string) []string {
	sMap := make(map[string]struct{})
	for _, s := range sl {
		sMap[s] = struct{}{}
	}
	reduced := make([]string, len(sMap))
	i := 0
	for k := range sMap {
		reduced[i] = k
		i++
	}
	return reduced
}

func MinQuine(s string) []string {
	// Repetitions in the initial s string don't count.
	words := uniqueStrings(strings.Split(s, " "))

	// No repetition can happen with a single word.
	if len(words) < 2 {
		return []string{}
	}
	// No N-1 common substring can happen in strings shorter than 2.
	if len(words[0]) < 2 {
		return []string{}
	}

	// At least 2 words, each at least 2 letters long.
	maxPos := len(words[0]) - 1 // Included and >= 1.
	counts := make(map[string]int)
	for _, word := range words {
		for i := 0; i <= maxPos; i++ {
			var smaller string
			if i == 0 {
				smaller = word[1:]
			} else if i == maxPos {
				smaller = word[:maxPos]
			} else {
				smaller = word[:i] + word[i+1:]
			}
			_, ok := counts[smaller]
			if ok {
				counts[smaller]++
			} else {
				counts[smaller] = 1
			}
		}
	}

	result := make([]string, 0, len(counts))
	for word, count := range counts {
		if count > 1 {
			result = append(result, word)
		}
	}

	sort.Strings(result)
	fmt.Println(s, result)
	return result
}