soln.py

# leetcode 30.
def find_word_concatenation(s, words):
    result_indices = []
    worddict = dict()
    wordlen = len(words[0])
    i, j = 0, 0
    total = 0
    for word in words:
        if word not in worddict:
            worddict[word] = 0
        worddict[word] += 1
        total += len(word)
    for i in range(len(s) - len(words) * wordlen + 1):
        seen = dict()
        for j in range(len(words)):
            start = i + j * wordlen
            w = s[start : start + wordlen]
            if w not in worddict:
                break
            if w not in seen:
                seen[w] = 0
            seen[w] += 1
            if seen[w] > worddict[w]:
                break
            # add start index to result if we are done with all the words
            if j + 1 == len(words):
                result_indices.append(i)
    return result_indices