How to make unique string out of substrings?-CodePudding

When I concatenate two strings (e.g. "q5q3q2q1" and "q5q4q3q2q1") I get string that have duplicate substrings q5,q3,q2,q1 which appears twice.

The resultant string would be "q5q3q2q1q5q4q3q2q1" and I need to have each substring (q[number]) appear once i.e."q5q4q3q2q1". Substring doesn't have to start with 'q', but I could set restriction that it doesn't start with number, also it could have multiple numbers like q11.

What could I use to get this string? If solution could be written in Java that would be good, otherwise only algorithm would be useful.

CodePudding user response：

You can split the concatenated string in groups and then use a set, if order of groups doesn't matter, or a dictionary if it is.

a = "q5q3q2q1"
b = "q5q4q3q2q1"

# Concatenate strings
c = a   b
print(c)

# Create the groups
d = ["q"   item for item in c.split("q") if item != ""]
print(d)

# If order does not matter
print("".join(set(d)))

# If order does matter
print("".join({key: 1 for key in d}.keys()))

CodePudding user response：

Another solution, this one is using regular expression. Concatenate the string and find all patterns ([^\d] \d ) (regex101). Then add found strings to set to remove duplicates and join them:

import re

s1 = "q5q3q2q1"
s2 = "q5q4q3q2q1"

out = "".join(set(re.findall(r"([^\d] \d )", s1   s2)))
print(out)

Prints:

q5q2q1q4q3

CodePudding user response：

Some quick way of doing this via java as you asked in question:

        String a = "q1q2q3";
        String b = "q1q2q3q4q5q11";
        List l1 = Arrays.asList(a.split("q"));
        List l2 = Arrays.asList(b.split("q"));
        List l3 = new ArrayList<String>();
        l3.addAll(l1);
        List l4 = new ArrayList<String>();
        l4.addAll(l2);
        l4.removeAll(l3);
        l3.addAll(l4);

        System.out.println(String.join("q", l3));

Output:

q1q2q3q4q5q11

CodePudding user response：

This is a variation of @DanConstantinescu's solution in JS:

Start with the concatenated string.
Split string at the beginning of a substring composed of text followed by a number. This is implemented as a regex lookahead, so split returns the string portions as an array.
Build a set from this array. The constructor performs deduplication.
Turn the set into an array again
Concat the elements with the empty string.

While this code is not Java it should be straightforward to port the idea to other (imperative or object-oriented) languages.

let s_concatenated = "q5q3q2q1"   "q5q4q3q2q1"   "q11a13b4q11"
  , s_dedup
  ;

s_dedup = 
    Array.from(
        new Set(s_concatenated
                   .split(/(?=[^\d] \d )/)  // Split into an array
            ) // Build a set, deduplicating
    ) // Turn the set into an array again
       .join('') // Concat the elements with the empty string.
    ;

console.log(`'${s_concatenated}' -> '${s_dedup}'.`);