here is my simple C++ solution // // //

string caesarCipher(string s, int k) { string res(""); int ch = 0;

for (auto c : s)
{
    if (isalpha(c))
    {
        int ch = int(c);
        ch += k;

        /* check where we are in relation to 1 -26 , taking into
        account of any Caps letter
        */
        int curr_index = isupper(c) ? (int(c) -65) : int(c) - 97;

        /* by how much are we going to be out of bound*/
        bool out_of_boundOffset = (k + curr_index > 25);

        if ( out_of_boundOffset )
            ch = isupper(c) ? (65 + (k + curr_index) % 26) : (97 + (k + curr_index) % 26);

        res.push_back(char(ch));
    }
    else {
        res.push_back(c);
    }
}
return res;

}

My python solution

s2 = ''
    for ch in s :
        if ch.isalpha():
            t = ord(ch)
            if 96 <= t <= 122 :
                t += k
                while t > 122 :
                    t -= 26
            elif 65 <= t <= 90 :
                t += k 
                while t > 90 :
                    t -= 26
            s2 += chr(t)
        else :
            s2 += ch
    return s2

static Map<Character, Integer> smallcharintmap = new HashMap<>();
static Map<Integer, Character> smallintcharmap = new HashMap<>();

static Map<Character, Integer> capscharintmap = new HashMap<>();
static Map<Integer, Character> capsintcharmap = new HashMap<>();

static {
    char smallstart = 'a';
    char capstart = 'A';

    for(int i=1;i<=26;i++) {
        smallcharintmap.put(smallstart, i);
        smallintcharmap.put(i, smallstart);
        smallstart++;

        capscharintmap.put(capstart, i);
        capsintcharmap.put(i, capstart);
        capstart++;
    }
}

public static String caesarCipher(String str, int k) {
    StringBuilder resultBuilder = new StringBuilder();
    for(int i = 0; i < str.length(); i++) {
        Character ch = str.charAt(i);
        if(Character.isAlphabetic(ch)) {
            if(Character.isLowerCase(ch)) {
                int key = (smallcharintmap.get(ch) + k)%26;
                resultBuilder.append(smallintcharmap.get(key == 0 ? 26 : key));
            } else if(Character.isUpperCase(ch)) {
                int key = (capscharintmap.get(ch) + k)%26;
                resultBuilder.append(capsintcharmap.get(key == 0? 26 : key));
            }
        } else {
            resultBuilder.append(ch);
        }
    }
    return resultBuilder.toString();
}

int base;
for(int i=0; i<s.size(); i++){
        if(isalpha(s[i])){
                if(islower(s[i])){
                        base = 'a';
                }else{
                        base = 'A';
                }
                s[i] = ((s[i] - base + k) % 26) + base;
        }
}
return s;

}