Educational Codeforces Round 53 (Rated for Div. 2)

 

http://codeforces.com/contest/1073

 

A. Diverse Substring

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define minv 1e-6
#define inf 1e9
#define pi 3.1415926536
#define nl 2.7182818284
const ll mod=1e9+7;//998244353
const int maxn=1e3+10;

char s[maxn];

int main()
{
    int n,i;
    scanf("%d",&n);
    scanf("%s",s);
    for (i=0;i<=n-2;i++)
        if (s[i]!=s[i+1])
            break;
    if (i==n-1)
        printf("NO");
    else
    {
        printf("YES\n");
        printf("%c%c",s[i],s[i+1]);
    }
    return 0;
}

 

B. Vasya and Books

#include <iostream>
#include <cstdio>
using namespace std;
const int maxn=2e5+10;

int f[maxn];

int main()
{
    int n,a,v=0,i;
    scanf("%d",&n);
    for (i=1;i<=n;i++)
    {
        scanf("%d",&a);
        f[a]=i;
    }
    for (i=1;i<=n;i++)
    {
        scanf("%d",&a);
        if (i!=1)
            printf(" ");
        if (f[a]<v)
            printf("0");
        else
            printf("%d",f[a]-v);
        v=max(f[a],v);
    }
    return 0;
}

 

C. Vasya and Robot

奇偶，负数取模

#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int maxn=2e5+10;
const ll inf=1e9;

int px[maxn],py[maxn];

int main()
{
    char c;
    int n,x,y,ax,ay,i,l,r,m,re;
    scanf("%d\n",&n);
    for (i=1;i<=n;i++)
    {
        scanf("%c",&c);
        if (c=='U')
            x=0,y=1;
        else if (c=='D')
            x=0,y=-1;
        else if (c=='L')
            x=-1,y=0;
        else
            x=1,y=0;
        px[i]=px[i-1]+x;
        py[i]=py[i-1]+y;
    }
    scanf("%d%d",&ax,&ay);
    if (px[n]==ax && py[n]==ay)
    {
        printf("0");
        return 0;
    }
    if (abs(ax+ay+n)%2==1)
    {
        printf("-1");
        return 0;
    }
    re=inf;
    for (i=1;i<=n;i++)
    {
        l=i;
        r=n;
        while (l<=r)
        {
            m=(l+r)>>1;
            ///change [i,m] ; use [1,i-1] [m+1,n]
            if (m-i+1>=abs(px[i-1]+px[n]-px[m]-ax)+abs(py[i-1]+py[n]-py[m]-ay))
                r=m-1;
            else
                l=m+1;
        }
        if (l!=n+1)
            re=min(re,l-i+1);
    }
    if (re==inf)
        re=-1;
    printf("%d",re);
    return 0;
}

 

D. Berland Fair

#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int maxn=2e5+10;

int nex[maxn],a[maxn];

int main()
{
    int n,i,j,g;
    ll m,tot=0,num=0;
    scanf("%d%lld",&n,&m);

    for (i=0;i<n;i++)
        scanf("%d",&a[i]),tot+=a[i];
    for (i=0;i<n;i++)
        nex[i]=(i+1)%n;
    g=n;
    i=0;
    j=n-1;
    while (nex[i]!=i)
    {
        num+=m/tot*g;
        m%=tot;
        while (nex[i]!=i)
        {
            if (a[i]<=m)
            {
                m-=a[i];
                num++;
                j=i;
            }
            else
            {
                nex[j]=nex[i];
                tot-=a[i];
                g--;
            }
            i=nex[i];
            if (m>=tot)
                break;
        }
    }
    num+=m/a[i];
    cout<<num;
    return 0;
}
/*
1 100
1

3 1000
1 2 100
*/

 

E. Segment Sum

代码是错的，以待后续埋坑

#include <bits/stdc++.h>
using namespace std;
#define ll long long
const ll mod=998244353;
const double minv=1e-10;

ll sum=0,shi[20],k,f[20][20];

void work(ll a,int w,int g,int hav,ll num,int ori,int cond)
{
    int s,gg,i,j,c;
    if (a==0)
        return;
    s=a/shi[w];
    for (i=0;i<=s;i++)
    {
        gg=g-(!((hav>>i) & 1) && (!(i==0 && ori==1)));
        if (gg>=0)
        {
            if (i<s)
            {
                /**
                这一位选的是i，
                除去这一位，还有w位，
                从gg个数中选j个数作为需要添加的数(之前没出现过的)，
                每一位都有k-gg+j种选择
                **/
                f[0][0]=1;
                for (j=1;j<=w;j++)
                {
                    f[j][0]=f[j-1][0]*(k-gg)%mod;
                    ///already k-gg numbers
                    sum=(sum+f[j-1][0]* sum of k-gg numbers )%mod;


                    for (c=1;c<=min(gg,j);c++)

                            sum=(sum+f[j-1][c]* k-gg+c numbers + f[j-1][c-1]* any number(random average of gg numbers))


                        f[j][c]=(f[j-1][c]*(k-gg+c)+f[j-1][c-1]*(10-(k-gg+c-1)))%mod;
                }
                for (c=0;c<=min(gg,w);c++)
                    sum=(sum+f[w][c]*cond)%mod;


                ///geshu
//                f[0][0]=1;
//                for (j=1;j<=w;j++)
//                {
//                    f[j][0]=f[j-1][0]*(k-gg)%mod;
//                    for (c=1;c<=min(gg,j);c++)
//                        f[j][c]=(f[j-1][c]*(k-gg+c)+f[j-1][c-1]*(10-(k-gg+c-1)))%mod;
//                }
//                for (c=0;c<=min(gg,w);c++)
//                    sum=(sum+f[w][c]*cond)%mod;
            }
            else
                work(a%shi[w],w-1,gg,hav|(1<<i),ori&(i==0),cond);
        }
    }
}

int main()
{
    ll l,r;
    int i,w;
    scanf("%lld%lld%d",&l,&r,&k);
    shi[0]=1;
    for (i=1;i<=18;i++)
        shi[i]=shi[i-1]*10;

    w=log(r+minv)/log(10);
    work(r,w,k,0,0,1,1);
    if (l!=1)
    {
        w=log(l-1+minv)/log(10);///l=1???
        work(l-1,w,k,0,0,1,-1);
    }
    printf("%lld",(sum+mod)%mod);
    return 0;
}