string difference

t10e16.stringdiff.cpp

// t10e16.stringdiff.cpp
// juanfc 2022-01-14
// 

#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;
}

int count(string s, char c);
TCharFreq getFreqs(string s)
{
    TCharFreq r;
    for (int i = 0; i < 256; ++i) {
        r[i] = count(s, i);
    }
    return r;
}
int count(string s, char c)
{
    int cnt = 0;
    for (int i = 0; i < s.size(); ++i) {
        if (s[i] == c) {
            ++cnt;
        }
    }
    return cnt;
}