Top Coder SRM 450

EnemyTowers.cs

using System;
class EnemyTowers
{
    const int INF = int.MaxValue;
    public int sim( int s, int h, int a, int t)
    {
        int ret = 0;
        int p = h;

        while( s > 0 && t > 0 ) {
            ret++;
            int d = s;
            p -= d;
            if( p <= 0 ) {
                t -= 1 + (-p / h);
                p = h - (-p % h);
            }
            s -= t * a;
        }
        return (s <= 0) ? INF : ret;
    }

    public int attack(int s, int h, int a, int wo, int st)
    {
        const int INF = int.MaxValue;
        int lb = 0, ub = s;

        int ret = INF;
        while (ub >= lb)
        {
            int mid = lb + (ub - lb) / 2;
            //Console.WriteLine("lb: {0}, ub: {1}, mid: {2}", lb, ub, mid);

            int swo = mid;
            int sst = (s - mid);
            int wsr = sim(swo, h, a, wo);
            int ssr = sim(sst, h, a, st);

            ret = Math.Min(ret, Math.Max(wsr, ssr));

            if (wsr > ssr) lb = mid + 1;
            else ub = mid - 1;
        }
        return(ret == INF) ? -1 : ret;
    }
}

var e = new EnemyTowers();
Console.WriteLine(e.attack(7, 2, 1, 2, 3));
Console.WriteLine(e.attack(120, 10, 40000, 6, 6));
Console.WriteLine(e.attack(119, 10, 40000, 6, 6));
Console.WriteLine(e.attack(200, 50, 3, 10, 5));
Console.WriteLine(e.attack(1000000000, 40000, 40000, 20223, 20226));
Console.WriteLine(e.attack(1000000000, 1, 1, 40000, 40000));

StrangeComputer.cs

class StrangeComputer
{
    public int setMemory(String mem)
    {
        var c = 0;
        char cur = '0';
        for( int i = 0; i < mem.Length; i++ )
            if( mem[i] != cur ) {
                if (cur == '0') cur = '1';
                else cur = '0';
                c++;
            }
        return c;
    }
}

StrangeComputer s = new StrangeComputer();

Console.WriteLine(s.setMemory("0011"));
Console.WriteLine(s.setMemory("000"));
Console.WriteLine(s.setMemory("0100"));
Console.WriteLine(s.setMemory("111000111"));