Arm Wrestling Tournament (UVALive 5060, Regionals 2010 >> Asia - Jakarta)

///     Raihan Ruhin
///     CSE, Jahangirnagar University.
///     Dhaka-Bangladesh.
///     id: raihanruhin (topcoder / codeforces / codechef / uva), 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 100010



int main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);
    int kk=1, tc, n, m, k, x;
    string s;
    cin>>tc;
    while(tc--)
    {
        vector<int>nowID, nextID, nowData, nextData, initial;
        cin>>n>>k;
        m=(1<<n);
        vector<int> child[m+2];
        initial.push_back(0);
        for(int i=1;i<=m;i++)
        {
            cin>>x;
            initial.push_back(x);
            nowData.push_back(x);
            nowID.push_back(i);
        }
        while(nowData.size()>1)
        {
            for(int i=0;i<nowData.size();i+=2)
            {

                if(nowData[i]>=nowData[i+1])
                {
                    nextData.push_back(min(initial[nowID[i]], nowData[i]-nowData[i+1]+k));
                    nextID.push_back(nowID[i]);
                    child[nowID[i]].push_back(nowID[i+1]);
                }
                else
                {
                    nextData.push_back(min(initial[nowID[i+1]], nowData[i+1]-nowData[i]+k));
                    nextID.push_back(nowID[i+1]);
                    child[nowID[i+1]].push_back(nowID[i]);
                }
            }

            nowData=nextData;
            nowID=nextID;
            nextData.clear();
            nextID.clear();
        }

        cout<<nowID[0]<<"\n";
        cout<<child[nowID[0]][0];
        for(int i=1;i<child[nowID[0]].size();i++)
            cout<<" "<<child[nowID[0]][i];
        cout<<"\n";
    }

    return 0;
}

Tariff Plan (UVA 12157, UVALive 4405, Regionals 2008 >> Asia - Kuala Lumpur)

///     Raihan Ruhin
///     CSE, Jahangirnagar University.
///     Dhaka-Bangladesh.
///     id: raihanruhin (topcoder / codeforces / codechef / uva), 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 100010

int main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);
    int kk=1, tc, n, m, duration;
    string s;
    cin>>tc;
    while(tc--)
    {
        int mile=0, juice=0;
        cin>>n;
        while(n--)
        {
            cin>>duration;
            mile+=(duration/30+1)*10;
            juice+=(duration/60+1)*15;
        }
        if(mile<juice) cout<<"Case "<<kk++<<": Mile "<< mile <<"\n";
        else if(juice<mile) cout<<"Case "<<kk++<<": Juice "<< juice <<"\n";
        else cout<<"Case "<<kk++<<": Mile Juice "<< mile <<"\n";
    }

    return 0;
}

Prime Path (UVA 12101, SPOJ PPATH, POJ 3126, HDU 1973, UVALive 3639, Regionals 2006 >> Europe - Northwestern)

///     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 10000

vector<int>prime;
bool status[MX+2];
int pl;

void PrimeGenerate(int n)
{
    int sq=sqrt(n);
    for(int i=3; i<=sq; i+=2)
    {
        if(!status[i])
            for(int j=i*i; j<=n; j+=(i<<1))
                status[j]=true;
    }

    status[0]=status[1]=true;
    for(int i=4;i<=n;i+=2) status[i]=true;

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

int dp[MX], st, ed, taken[MX], dist[10010];
vector<int>v[10010];

int bfs(int num)
{
    if(num==ed) return 1;
    dist[num]=1;
    queue<int>Q;
    Q.push(num);
    while(!Q.empty())
    {
        int qq=Q.front();
        Q.pop();
        for(int i=0;i<v[qq].size();i++)
            if(!dist[v[qq][i]])
            {
                dist[v[qq][i]]=dist[qq]+1;
                if(v[qq][i]==ed) return dist[v[qq][i]];
                Q.push(v[qq][i]);
            }
    }
return 100000;
}

int main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);
    int tc, kk=1, n;
    PrimeGenerate(MX);
    int loopst;

    pl=prime.size();
    for(int i=0;i<pl;i++)
        if(prime[i]>999)
        {
            loopst=i;
            break;
        }

    for(int i=loopst;i<pl;i++)
    {

        for(int j=loopst;j<pl;j++)
        {
            int tmp=prime[i];
            int tmp2=prime[j], cnt=0;

            while(tmp && tmp2)
            {
                if(tmp%10 != tmp2%10) cnt++;
                tmp/=10;
                tmp2/=10;
            }

            if(cnt==1)
            {
                v[prime[i]].push_back(prime[j]);
            }
        }
    }

    cin>>tc;
    while(tc--)
    {
        cin>>st>>ed;
        if(ed>st) swap(st, ed);
        CLR(dist);
        int ans=bfs(st);
        if(ans<100000) cout<<ans-1<<"\n";
        else cout<<"Impossible\n";
    }

return 0;
}

Hours and Minutes (UVA 12531, UVALive 6138, Regionals 2012 >> Latin America)

///     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;
    while(cin>>n)
    {
        if(n%6) cout<<"N\n";
        else cout<<"Y\n";
    }

return 0;
}