Trie data structure

Question

Given N strings. Each string contains only lowercase letters from a−j (both inclusive). The set of N strings is said to be GOOD SET if no string is prefix of another string else, it is BAD SET.

For example, aab, abcde, aabcd is BAD SET because aab is prefix of aabcd.

Print GOOD SET if it satisfies the problem requirement. Else, print BAD SET and the first string for which the condition fails.

Input Format:
First line contains N, the number of strings in the set. Then next N lines follow, where ith line contains ith string.

Constraints:
1 ≤ N ≤ 105 1 ≤ Length of the string ≤60

Output Format:
Output GOOD SET if the set is valid.
Else, output BAD SET followed by the first string for which the condition fails.

Can anyone suggest on this?

Answer 1

构造一个trie，将每个字符串逐个插入到trie中，记录指向表示插入trie中的每个字符串的节点的指针。完成后，扫描节点指针以查找所有字符串。如果其中任何一个在内部节点结束，那么它就是BAD SET。否则，（所有字符串在不同的叶子上结束），它是一个好的集合。时间和空间复杂度都与所有字符串的总长度成线性关系。