  The closest string problem is an NP-hard problem, whose task is to find a
string that minimizes maximum Hamming distance to a given set of strings. This
can be reduced to an integer program (IP). However, to date, there exists no
known polynomial-time algorithm for IP. In 2004, Meneses et al. introduced a
branch-and-bound (B & B) method for solving the IP problem. Their algorithm is
not always efficient and has the exponential time complexity. In the paper, we
attempt to solve efficiently the IP problem by a greedy iterative rounding
technique. The proposed algorithm is polynomial time and much faster than the
existing B & B IP for the CSP. If the number of strings is limited to 3, the
algorithm is provably at most 1 away from the optimum. The empirical results
show that in many cases we can find an exact solution. Even though we fail to
find an exact solution, the solution found is very close to exact solution.
