【面试题】串联所有单词的子串，找到所有符合条件的串联子串的起始索引

// Helper function to check if two hash tables are equal
int areHashTablesEqual(int *hash1, int *hash2, int size) {
    for (int i = 0; i < size; i++) {
        if (hash1[i] != hash2[i]) {
            return 0;
        }
    }
    return 1;
}

void findSubstring(char *s, char **words, int wordsSize, int wordLen, int *result, int *returnSize) {
    int sLen = strlen(s);
    int concatLen = wordsSize * wordLen;
    int *wordCount = (int *)calloc(256, sizeof(int));
    int *windowCount = (int *)calloc(256, sizeof(int));

    // Initialize wordCount hash table
    for (int i = 0; i < wordsSize; i++) {
        for (int j = 0; j < wordLen; j++) {
            wordCount[(unsigned char)words[i][j]]++;
        }
    }

    for (int i = 0; i <= sLen - concatLen; i++) {
        memset(windowCount, 0, 256 * sizeof(int));
        int j;
        for (j = 0; j < wordsSize; j++) {
            char *word = s + i + j * wordLen;
            for (int k = 0; k < wordLen; k++) {
                windowCount[(unsigned char)word[k]]++;
            }
        }
        if (areHashTablesEqual(wordCount, windowCount, 256)) {
            result[(*returnSize)++] = i;
        }
    }

    free(wordCount);
    free(windowCount);
}

int* findSubstringIndices(char *s, char **words, int wordsSize, int *returnSize) {
    int wordLen = strlen(words[0]);
    int *result = (int *)malloc(sizeof(int) * 1000); // Allocate enough space for result
    *returnSize = 0;

    findSubstring(s, words, wordsSize, wordLen, result, returnSize);
    return result;
}