69. Sqrt(x)

    /*
     * 69. Sqrt(x)
     * 2016-5-10 by Mingyang
     * Just binary search  and logn complexity
     */
     public static int sqrt(int x) {
            long i = 0;
            long j = x / 2 + 1;
            while (i <= j) {
                long mid = (i + j) / 2;
                if (mid * mid == x)
                    return (int)mid;
                if (mid * mid < x)
                    i = mid + 1;
                else
                    j = mid - 1;
            }
            return (int)j;
        }
}