CharSequence

#include <iostream>
#include <cstring>

using namespace std;

class Character {
private:
    char cha;
public:
    Character(char c = 0) { cha = c; }

    friend ostream &operator<<(ostream &out, const Character &c) {
        out << c.cha;
        return out;
    }

    bool operator==(const Character &c) {
        return cha == c.cha;
    }

    Character toUpper() {
        cha = toupper(cha);
        return cha;
    }

    Character toLower() {
        cha = tolower(cha);
        return cha;
    }

};

class CharSequence {
private:
    Character *seq;
    int len;

public:
    CharSequence(const char *s = "") {
        len = strlen(s);
        seq = new Character[len + 1];
        for (int i = 0; i < len; ++i) {
            seq[i] = s[i];
        }
        seq[len] = Character('\0');
    }

    ~CharSequence() { delete[] seq; }

    // Copy-Constructor
    CharSequence(const CharSequence &cs) {
        len = cs.len;
        seq = new Character[len + 1];
        for (int i = 0; i < len; ++i) {
            seq[i] = cs.seq[i];
        }
        seq[len] = Character('\0');
    }

    // Assignement Operator
    CharSequence &operator=(const CharSequence &cs) {
        if (this == &cs) return *this;
        delete[] seq;
        len = cs.len;
        seq = new Character[len + 1];
        for (int i = 0; i < len; ++i) {
            seq[i] = cs.seq[i];
        }
        seq[len] = Character('\0');
        return *this;
    }

    CharSequence &operator+=(const Character &c) {
        Character *old = seq;
        seq = new Character[len + 1 + 1];
        for (int i = 0; i < len; ++i) {
            seq[i] = old[i];
        }
        seq[len++] = c;
        seq[len] = Character('\0');
        return *this;
    };

    bool operator==(const CharSequence &cs) {
        bool flag = true;
        if (len != cs.len) return false;
        for (int i = 0; i < len; ++i) {
            if (!(seq[i] == cs.seq[i])) {
                flag = false;
            }
        }
        return flag;
    }

    Character &operator[](int i) {
        return seq[i];
    }

    friend ostream &operator<<(ostream &out, const CharSequence &str) {
        for (int i = 0; i < str.len; ++i) {
            out << str.seq[i];
        }
        return out;
    }

    int operator[](char c) {
        int count = 0;
        for (int i = 0; i < len; ++i) {
            if (seq[i] == c) {
                count++;
            }
        }
        return count;
    }

    CharSequence toUpperCase() {
        CharSequence cs(*this);
        for (int i = 0; i < len; ++i) {
            cs.seq[i] = seq[i].toUpper();
        }
        return cs;
    }

    CharSequence toLowerCase() {
        CharSequence cs(*this);
        for (int i = 0; i < len; ++i) {
            cs.seq[i] = seq[i].toLower();
        }
        return cs;
    }
};


int main() {
    CharSequence cs;
    cs += Character('a');
    cout << cs;
    return 0;
}