Problem

We are given a string and we need to find if the string has unique characters in it.

Examples:

input: dev.to
output: true

input: javascript
output: false

Solution

The solution to this problem is very simple. It involves the usage of the set data structure. We iterate over the string and store the characters of the string in a set. Every time we store a character, we will check if the character already exist in the set. If we find that the character has already been stored in the set, this means that we encountered the character a while back in the string. Thus the string does not have unique characters hands with return false. If we reach till the end of the string and do not find any duplicate occurrences this means that the string is unique and we return true.

bool is_string_unique(string s) {
  set<char> store;
  for (auto a : s) {
    if (store.find(a) != store.end()) {
      // charecter already exists
      return false;
    }
    store.insert(a);
  }
  return true;
}

References: Cracking the Coding Interview - Gayle Laakmann McDowell
Have a nice day 😄