counting char freqs

t11e16.stringdiff.cpp

// t11e16.stringdiff.cpp
// juanfc 2023-11-22
// https://gist.github.com/c9714ca8843727fa6bf179ae6923ca1a

#include <iostream>
#include <array>
using namespace std;

string diff(string a, string b);

int main()
{

    cout << diff("telephone", "phonograph") << endl;
    cout << diff("holograph", "dog") << endl;
    return 0;
}

typedef array<int,256> TCharFreq;
TCharFreq getFreqs(string s);

string diff(string a, string b)
{
    string res;
    TCharFreq freqs_b = getFreqs(b);

    for ( int i = 0; i < a.size(); ++i )
        if (freqs_b[a[i]])
            --freqs_b[a[i]];
        else
            res += a[i];
    return res;
}


TCharFreq getFreqs(string s)
{
    TCharFreq r;
    for (int i = 0; i < 256; ++i)
        r[i] = 0;

    for (int i = 0; i < s.length(); ++i)
        ++r[s[i]];
    return r;
}