TopCoder SRM581: SurveillanceSystem

public class SurveillanceSystem {
    public string getContainerInfo(string containers, int[] reports, int L) {
        int n = containers.Length;
        var ans = Enumerable.Repeat('-', n).ToArray();
        var cand = Enumerable.Range(0, n - L + 1)
            .Select(i =>
                new {
                    from = i,
                    to = i + L,
                    containerNum = containers.Skip(i).Take(L).Count(c => c == 'X')
                }
            ).ToArray();

        for (int i = 0; i < n; i++) {
            if (cand.Where(c => c.from <= i && i < c.to && reports.Contains(c.containerNum)).Any()) {
                ans[i] = '?';
            }
            for (int j = 0; j <= L; j++) {
                int outOfRangeCandNum = cand.Count(c => c.containerNum == j && !(c.from <= i && i < c.to));
                if (outOfRangeCandNum < reports.Count(r => r == j))
                    ans[i] = '+';
            }
        }

        return new string(ans);
    }
}