Method pow

49. Group Anagrams/Solution.cpp:54–62

O(1)

    // O(1)
    unsigned long pow(unsigned long x, unsigned int y) {
        // bitwise traverse y
        unsigned long res = 1;
        for (int offset = sizeof(int) * 8 - 1; offset >= 0; offset --) {
            res *= res; // right shift
            if (y & (1 << offset)) res *= x;
        }
        return res;
    }
};

int main() {