7

Shortest Unique Prefix

Difficulty: MEDIUM
Contributed By
Prateek Kalyani
Avg. time to solve
15 min
Success Rate
85%

Problem Statement
Suggest Edit

You are given an array containing ‘N’ words. For each word, you need to find its shortest prefix which can uniquely identify it. For example “abcd” and “abdc” both have the prefix “ab” in common so we can’t uniquely find a word using the prefix “ab”. To uniquely identify both the words we need the prefix “abc” from “abcd” and “abd” from “abdc”.

Note:
You can assume that the words are unique. It means that it is always possible to find a unique prefix for each word.
Input Format:
The first line of the input contains an integer ‘T’ denoting the number of test cases.
The next ‘2*T’ lines describe the ‘T’ test cases.

The first line of each test case contains single positive integers ‘N’ denoting the number of words.
The next ‘N’ lines contain a string of lower case characters.
Output Format:
The output of each test case should contain 'N' lines, in the ith line you need to print the shortest unique prefix for ith word.

Print the output of each test case in a separate line.
Note:
You do not need to print anything, it has already been taken care of. Just implement the given function.
Constraints:
1 <= T <= 50
1 <= N <= 10^4  

Where ‘T’ is the number of test cases, ‘N’ is the number of words and, the sum of the lengths of all the words in a test case is less than 10^4.

Time Limit: 1 sec
Sample Input 1:
2
2
abcd
acdb
3
many
mango
mad
Sample Output 1:
ab
ac
many
mang
mad
Explanation for sample input 1:
Test case 1:
The string “abcd” and “acbd” have a common prefix “a” which can’t be used as a unique prefix so to make a unique prefix we will add one more character to “a” from each word. The “ab” for “abcd” and prefix “ac” for “acbd” is now the shortest and unique prefix.


Test case 2:
For string “many” the prefix “m” and “ma” is common in“mango” and “mad”. Similarly “man” is again common in “mango”. “Many” itself will be the unique shortest prefix.

For string “mango” we have the string ”many” such that “man” is common in both of them so for “mango” the prefix “mang” will the unique shorted prefix.

For string “mad” we have strings “many” and “mango” such that   “ma” is common in all of them. “Mad” itself will be a unique shortest prefix.
Sample Input 2:
2
3
sample
same
sort
2
quick
merge
Sample Output 2:
samp
same
so
q
m
Reset Code
Full screen
copy-code
Console