[C++]Check Elements Containing Prefix in Vector

Let’s initialize the vector like this:

vector <string> vec {"620", "762074223", "6205524421"};

The first element in the vector is the prefix, and the rest may have the prefix or not. If an element has the prefix, return TRUE.

For better performance, you can use std::sort(). Then, check if the elements have the prefix with string::find().

bool solution(vector<string> vec) {

    bool answer = false;

    sort(vec.begin(), vec.end());

    for(int i = 0; i < vec.size()-1; i++){
        if(vec[i+1].find(vec[0]) == 0){
            answer = true;
        }
    }

    return answer;
}

string::substr() also can be used to check the elements like this:

if ( vec[i] == vec[i+1].substr(0, vec[i].size()))

Performance difference between two methods is described [here]