Getting started with Codeforces: Part 2: Find out easiest problem.

It's always better to start with the easiest problems first. To find easiest problems, follow the steps.

Step 1: First of all, login to you account. [read previous post for registration and login]

Step 2: Click on "PROBLEMSET" tab. or go http://codeforces.com/problemset directly.

Step 2: You will see a list of problems sorted according to the problem added date.

Step 3: But this is not the easiest list. Problems with maximum solve is the easiest. to sort the problem list according to maximum number of solve, click on the Solved button as marked red in the picture below.

You will notice the list has changed. This is the easiest list. You can also find the list by the following link.
http://codeforces.com/problemset?order=BY_SOLVED_DESC

Step 4: Click on the first problem. That's the easiest to start with.

Next Post: Understanding your first problem (Theatre Square) in codeforces.

Getting started with Codeforces: Part 1: Opening an account

Step 1: Open your browser. Type codeforces.com and hit enter.

Step 2: You will see similar page as picture below. Click on Register button (marked in red circle in the picture below) or goto http://codeforces.com/register directly.

Step 3: Now Fill-up the form and then click Register button below.
Here, 'Handle' is your desire username. If your desire username is already taken try a new one. Don't forget your username, it will require each time you login to codeforces. Email is your active email account. In Password, type a new password for your codeforces id, write the same password again in Confirm Password box.

Step 4: After clicking register button, codeforces will send an email verification link in your email account. Login to your email, open the mail (inbox or spam folder) and click on the activation link. .
Your account is ready to use now.

Step 5: After your account being activated, you can go to codeforces.com and click Enter (marked red in the picture below) to login to your account.
You could also use http://codeforces.com/enter directly.

Step 6: Type your Handle (username) and password as you put in the form while registration. And click Login button. You could also check "Remember me for a month" if you wish to login automatically in your browser for next 30 days.

After successful login, you will see your Username and Logout button instead of Enter and Register button as below.

Now, you have created and logged in to your codeforces account successfully.


Next Post: How to find out the easiest problem in codeforces for practicing.

Fermat's Chirstmas Theorem ( UVALive 4088, Regionals 2007 >> Africa/Middle East - Arab and North Africa)

///     Raihan Ruhin
///     CSE, Jahangirnagar University.
///     Dhaka-Bangladesh.
///     id: raihanruhin (topcoder / codeforces / codechef / uva / uvalive / spoj), 3235 (lightoj)
///     mail: raihanruhin@ (yahoo / gmail / facebook)
///     blog: ruhinraihan.blogspot.com

#include<bits/stdc++.h>
using namespace std;

#define SET(a) memset(a,-1,sizeof(a))
#define CLR(a) memset(a,0,sizeof(a))
#define PI acos(-1.0)

#define MOD 1000000007
#define MX 1000005

bool stats[MX];
vector<int>prime;
vector<int>sqp;


void PrimeGenerate(int n)
{
    int sq=sqrt(n);
    for(int i=3; i<=sq; i+=2)
    {
        if(!stats[i])
            for(int j=i*i; j<=n; j+=i+i)
                stats[j]=true;
    }
    for(int i=2;i<=n;i+=2) stats[i]=true;

    prime.push_back(2);
    for(int i=3; i<=n; i+=2)
        if(!stats[i])
            prime.push_back(i);
return;
}

void squareRootGen(int n)
{
    int sq=sqrt(n);
    for(int i=1;i<=sq;i++)
        for(int j=i+1;j<=sq;j+=2)
        {
            int mul=i*i+j*j;
            if(mul>1000000) break;
            if(!stats[mul])
                sqp.push_back(mul);
        }
return;
}

int main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);
    int tc, kk=1, n, L, U, x, y;
    string s;
    char ch;
    PrimeGenerate(1000000);
    squareRootGen(1000000);
    sqp.push_back(2);
    sort(sqp.begin(), sqp.end());
    while(cin>>L>>U)
    {
        if(L==-1 && U==-1) break;
        int x = upper_bound(prime.begin(), prime.end(), U) - lower_bound(prime.begin(), prime.end(), L);
        int y = upper_bound(sqp.begin(), sqp.end(), U) - lower_bound(sqp.begin(), sqp.end(), L);
        cout<< L <<" "<<U<<" "<<x<<" "<<y<<"\n";
    }
return 0;
}

Wooden Sticks (UVALive 2322, ZOJ 1025, HDU 1051, POJ 1065, SPOJ MSTICK, Regionals 2001 >> Asia - Taejon)

///     Raihan Ruhin
///     CSE, Jahangirnagar University.
///     Dhaka-Bangladesh.
///     id: raihanruhin (topcoder / codeforces / codechef / uva / uvalive / spoj), 3235 (lightoj)
///     mail: raihanruhin@ (yahoo / gmail / facebook)
///     blog: ruhinraihan.blogspot.com

#include<bits/stdc++.h>
using namespace std;

#define SET(a) memset(a,-1,sizeof(a))
#define CLR(a) memset(a,0,sizeof(a))
#define PI acos(-1.0)

#define MOD 1000000007
#define MX 100000


int main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);
    int tc, kk=1, n;
    pair<int, int> pii[5002];
    bool vis[5002];
    string s;
    char ch;
    cin>>tc;
    while(tc--)
    {
        CLR(vis);
        cin>>n;
        for(int i=0;i<n;i++)
            cin>>pii[i].first>>pii[i].second;
        sort(pii, pii+n);
        int cnt=0;
        for(int i=0;i<n;i++)
        {
            if(!vis[i])
            {
                cnt++;
                vis[i]=true;
                int cur=i;
                for(int j=i+1;j<n;j++)
                    if(!vis[j])
                        if(pii[j].second>=pii[cur].second)
                        {
                            vis[j]=true;
                            cur=j;
                        }
            }

        }
        cout<< cnt <<"\n";
    }
return 0;
}

Change (UVaLive 3004, Regionals 2004 >> South Pacific)

///     Raihan Ruhin
///     CSE, Jahangirnagar University.
///     Dhaka-Bangladesh.
///     id: raihanruhin (topcoder / codeforces / codechef / uva / uvalive / spoj), 3235 (lightoj)
///     mail: raihanruhin@ (yahoo / gmail / facebook)
///     blog: ruhinraihan.blogspot.com

#include<bits/stdc++.h>
using namespace std;

#define SET(a) memset(a,-1,sizeof(a))
#define CLR(a) memset(a,0,sizeof(a))
#define PI acos(-1.0)

#define MOD 1000000007
#define MX 100000


int main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);
    int tc, kk=1, n, notes[]={2000, 1000, 500, 200, 100, 50, 20, 10, 5}, cst, ofr, chg;
    double cost, offer;
    string s;
    char ch;
    while(cin>>cost>>offer)
    {
        cost+=.005, offer+=.005;
        cost*=100.0, offer*=100.0;
        cst=cost, ofr=offer;
        //cout<<offer<<" "<<cst<<endl;
        if(cst==0 && ofr==0) break;
        if(cst%5==1) cst-=1;
        else if(cst%5==2) cst-=2;
        else if(cst%5==3) cst+=2;
        else if(cst%5==4) cst+=1;

        if(cst>ofr) cout<<"Not enough money offered.\n";
        else if(cst==ofr) cout<<"Exact amount.\n";
        else
        {
            chg=ofr-cst;

            int space=0;
            for(int i=0;i<9;i++)
            {
                int cnt=0;
                while(chg>=notes[i])
                {
                    cnt++;
                    chg-=notes[i];
                }
                if(cnt)
                {
                    if(space) cout<<" ";
                    space=1;
                    if(i<5)
                        cout<<"$"<<notes[i]/100<<"*"<<cnt;
                    else
                        cout<<notes[i]<<"c*"<<cnt;
                }
            }
            cout<<"\n";
        }

    }
return 0;
}