372. Super Pow

    /*
     * 372. Super Pow
     * 2016-7-16 by Mingyang
     */
      private int mod = 1337;
        public int superPow(int a, int[] b) {
            int n = b.length;
            int ans = 1;
            for (int i = n - 1; i >= 0; i--) {
                ans = ans * quick_pow(a, b[i]) % mod;
                a = quick_pow(a, 10);
            }
            return ans;
        }    
        int quick_pow(int a, int b) {
            int ans = 1;
            a %= mod;
            while (b > 0) {
                if ((b & 1) !=0) ans = ans * a % mod;
                a = a * a % mod;
                b >>= 1;
            }
            return ans;        
        }