Problem link = https://www.naukri.com/code360/problems/convert-to-hexadecimal_1102544

My solution is following

string toHex(int num) {
    string ans = "";

    // Loop through the integer in 4-bit chunks
    for (int i = 28; i >= 0; i -= 4) 
    {
        // Lines of conflict
        /***********************************************/
        // Extract 4 bits starting from bit position i
        int number_before = (num  & (15 << i));
        number_before = (number_before >> i) ;
        /***********************************************/



        // Convert to hexadecimal character and append to result string
        if(number_before == 0 && ans.size() == 0) continue;
        else if (number_before < 10) {
            ans += (char)(number_before + '0');  // Convert 0-9 to '0'-'9'
        } else {
            ans += (char)(number_before - 10 + 'A');  // Convert 10-15 to 'A'-'F'
        }
    }

    return ans;
}

        int number_before = (num  & (15 << i));
        number_before = (number_before >> i) ;

        int number_before = ((num>> i) & 15 );

Two statements are provided in above question as mentioned above.

In this problem i try to record group of 4 bits at once in number “number_before” from number “num”. “num” can be positive & negative. Second statement is working correctly as expected. But first is producing unexpected results .Can anyone tell the reason why ?