Question

我收到了一个String（目录路径）的集合。如何获得所有字符串的最长公共前缀？

实施例： [“e：/ users / test”，“e：/ users / test / abc /”，“c：/ programs”，“e：/ data”，“/ test”]

解决方案必须是： [“e：/”，“c：/ programs”，“/ test”]

我不知道如何实现这个......

感谢您的帮助，问候

Answer 1

既不漂亮也不快，但似乎有效：

public List<String> longestCommonPrefixes(Collection<String> c) {
    List<String> list = new ArrayList<>(c);
    List<String> result = new ArrayList<>();
    while (!list.isEmpty()) {
        String lcp = longestCommonPrefix(list);
        result.add(lcp);
        for (Iterator<String> it = list.iterator(); it.hasNext();) {
            if (it.next().startsWith(lcp)) {
                it.remove();
            }
        }
    }
    return result;
}

private String longestCommonPrefix(List<String> list) {
    Map<Character, Integer> map = new HashMap<>();
    for (String s : list) {
        char c = s.charAt(0);
        if (map.containsKey(c)) {
            map.put(c, map.get(c) + 1);
        } else {
            map.put(c, 1);
        }
    }
    char c = 0;
    int max = 0;
    for (Map.Entry<Character, Integer> e : map.entrySet()) {
        int n = e.getValue();
        if (n > max) {
            max = n;
            c = e.getKey();
        } else if (n == max) {
            c = 0;
        }
    }
    if (c == 0) {
        int maxLen = 0;
        String sMaxLen = null;
        for (String s : list) {
            if (s.length() > maxLen) {
                maxLen = s.length();
                sMaxLen = s;
            } else if (s.length() == maxLen) {
                sMaxLen = null;
            }
        }
        return sMaxLen;
    } else {
        String s = null;
        for (int i = 0; i < list.size(); i++) {
            if (list.get(i).charAt(0) == c) {
                s = list.get(i);
                for (int j = i + 1; j < list.size(); j++) {
                    String s2 = list.get(j);
                    if (s2.charAt(0) != c) {
                        continue;
                    }
                    if (s.length() > s2.length()) {
                        s = s.substring(0, s2.length());
                    }
                    for (int k = 0; k < s.length(); k++) {
                        if (s.charAt(k) != s2.charAt(k)) {
                            s = s.substring(0, k);
                            break;
                        }
                    }
                }
                break;
            }
        }
        return s;
    }
}

Java String-Collection：最长的公共前缀

1 个答案: