3226. Number of Bit Changes to Make Two Integers Equal

class Solution {
public:
    int minChanges(int n, int k)
    {
        if (n == k) return 0;

        string n1 = bitset<32>(n).to_string();
        string k1 = bitset<32>(k).to_string();

        int cnt = 0;
        for (int i = 0; i < 32; i++)
        {
            if (n1[i] != k1[i] && n1[i] == '0') return -1;
            else if (n1[i] != k1[i] && n1[i] == '1') ++cnt;
        }
        return cnt;
    }
};

• T: $O(1)$
• S: $O(1)$