func findSubstring(s string, words []string) []int {
    var result []int
    if len(s) == 0 || len(words) == 0 {
        return result
    }
    wordMap := generateWordMap(words)
    start := -1
    stepSize := len(words[0])
    i := 0
    wordCount := 0
    for i < len(s) {
        if i+stepSize > len(s) {
            if start > -1 {
                i = start + 1
                start = -1
                wordMap = generateWordMap(words)
                wordCount = 0
                continue
            } else {
                break
            }
        }
        subStr := string(s[i:i+stepSize])
        if wordMap[subStr] > 0 {
            wordMap[subStr]--
            wordCount++
            if start == -1 {
                start = i
            }
            i += stepSize
        } else if start == -1 {
            i++
        } else {
            i = start + 1
            wordMap = generateWordMap(words)
            start = -1
            wordCount = 0
        }
        if wordCount == len(words) {
            result = append(result, start)
            i = start + 1
            wordMap = generateWordMap(words)
            start = -1
            wordCount = 0
        }
    }

    return result
}

func generateWordMap(words []string) (wordMap map[string]int) {
    wordMap = make(map[string]int)
    for _, word := range words {
        wordMap[word] = wordMap[word] + 1
    }
    return wordMap
}