Search code examples
c++unordered-mapunordered-set

unordered_set count function returns wrong value

Why does set.count('a') output 1 when there are 3 a's?

Program:

bool isAnagram(string s, string t) {

    unordered_set<char> set;

    for(int i=0; i<s.size(); i++){
        set.insert(s[i]);
    }

    cout << endl << set.count('a') << endl;
    return false;
}

Input:

s = 'anagram'

Output:

1
Solution

  • There's only one a in the set. If you want multiple as you need to use a multiset.

    Example:

    #include <iostream>
#include <set>
#include <string>

size_t count_char(const std::string& s, char ch) {
    // fill the set directly using the strings begin and end iterators
    std::multiset<char> set(s.begin(), s.end());

    return set.count(ch);
}

int main() {
    std::cout << count_char("anagram", 'a') << '\n';
}

    Output:

    3