Google Code Jam 2018 Qualification Round codes

a.cpp

#include <iostream>
using namespace std;
int main()
{
    int T;
    cin >> T;
    for (int kase = 1; kase <= T; ++kase)
    {   int d;
        int limit = 0, cur = 0, cha = 1, ans = 0;
        string s;
        cin >> d >> s;
        for (int i = 0; i < s.length(); ++i)
        {   if (s[i] == 'S')
            {   cur += cha;
                limit += 1;
            }
            else
                cha <<= 1;
        }
        if (d < limit) { cout << "Case #" << kase << ": IMPOSSIBLE"  << endl; continue;}

        if (s[s.length() -1] == 'C') cha >>= 1;
        

        for (int i = s.length() - 2; i >= 0; i--)
        {
            if (cur <= d)
            {
                cout << "Case #" << kase << ": " <<  ans << endl;
                break;
            }
            if (s[i] == 'C' && s[i+1] == 'S')
            {
                cur -= (cha >> 1);
                s[i] = 'S';
                s[i+1] = 'C';
                i += 2;
                ans++;
            }
            else if (s[i] == 'C')
                cha >>= 1;
        }
    }
}

b.cpp

#include <iostream>
#include <algorithm>
using namespace std;
int main()
{
    std::ios::sync_with_stdio(false);
    int T;
    cin >> T;
    for (int kase = 1; kase <= T; kase++)
    {   
        int n, ok = -1;
        cin >> n;
        int a[n], b[n];
        for (int i = 0; i < n; ++i) cin >> a[i];
        for (int i = 0; i < n; i += 2) b[i/2] = a[i];
        sort(b, b+(n/2)+(n%2));
        for (int i = 0; i < n; i += 2) a[i] = b[i/2];

        for (int i = 1; i < n; i += 2) b[i/2] = a[i];
        sort(b, b+(n/2));
        for (int i = 1; i < n; i += 2) a[i] = b[i/2];

        for (int i = 0; i < n-1; ++i)
            if (a[i] > a[i+1])
            {   ok = i;
                break;
            }
        cout << "Case #" << kase << ": "; 
        if (ok == -1) cout << "OK" << endl;
        else cout << ok << endl;

    }
}

c.cpp

#include <iostream>
#include <cstring>
#include <cmath>
using namespace std;
int main()
{
    int T;
    cin >> T;
    for (int kase = 1; kase <= T; ++kase)
    {
        int a;
        cin >> a;
        int x = (int)(sqrt(a));
        int y = ceil( (float)a / x );
        bool filled[x][y];
        memset(filled, 0, sizeof(filled));

        for (int tt = 0; tt < 1000; ++tt)
        {
           int bestx = 1, besty = 1;
           int empty = 0;
        
            for (int i = 1; i < x-1; i++)
                for (int j = 1; j < y-1; j++)
                {
                    int current = 0;
                    for (int k = -1; k <= 1; k++)
                        for (int l = -1; l <= 1; l++)
                            current += !filled[i+k][j+l];
                    if (current > empty)
                    {
                        bestx = i;
                        besty = j;
                        empty = current;
                    }
                }

            cout << bestx+1 << " " << besty+1 << endl;

            int fillx, filly;
            cin >> fillx >> filly;
            if (fillx == filly && filly == 0)
                break;

            if (fillx == filly && filly == -1)
                break;

            filled[fillx-1][filly-1] = true;

       }
    }
}