noip2015题解

没有正解，都是我的暴力

T1神奇的幻方

模拟

#include<iostream>
#include<cmath>
#include<ctime>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#define LL long long
#define N 1609
using namespace std;

int n;

int h[N],l[N];

int a[42][42];

int main()
{
    scanf("%d",&n);
    h[1]=1;l[1]=(n+1)/2;a[h[1]][l[1]]=1;
    int p;p=n*n;
    for(int i=2;i<=p;i++)
    {
        int t=i-1;
        if(h[t]==1&&l[t]!=n)
        {
            a[n][l[t]+1]=i;
            h[i]=n;l[i]=l[t]+1;
            continue;
        }
        if(l[t]==n&&h[t]!=1)
        {
            a[h[t]-1][1]=i;
            h[i]=h[t]-1;
            l[i]=1;
            continue;
        }
        if(h[t]==1&&l[t]==n)
        {
            a[h[t]+1][l[t]]=i;
            h[i]=h[t]+1;
            l[i]=l[t];
            continue;
        }
        if(h[t]!=1&&l[t]!=n)
        {
            if(a[h[t]-1][l[t]+1]==0)
            {
                a[h[t]-1][l[t]+1]=i;
                h[i]=h[t]-1;
                l[i]=l[t]+1;
            }else
            {
                a[h[t]+1][l[t]]=i;
                h[i]=h[t]+1;
                l[i]=l[t];
            }
        }
    }
    for(int i=1;i<=n;i++)
    {
        for(int j=1;j<=n;j++)
         printf("%d ",a[i][j]);
        printf("
");
    }
    return 0;
}

T2信息传递

模拟+卡时

#include<iostream>
#include<cmath>
#include<ctime>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#define LL long long
#define N 200005
using namespace std;

int n,ans,js;

int a[N];

int main()
{
    scanf("%d",&n);ans=n;
    for(int i=1;i<=n;i++) scanf("%d",&a[i]);
    for(int i=1;i<=n;i++)
    {
        int now;now=i;
        for(int j=1;j<=n;j++)
        {
            now=a[now];js++;
            if(now==i)
            {
                ans=min(ans,j);
                break;
            }
        }
        if(js>=4384380)break;
    }
    printf("%d
",ans);
    return 0;
}

Tarjian求最小环

#include<iostream>
#include<cmath>
#include<ctime>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#define LL long long
#define N 200005
using namespace std;

int n,top;

int sumedge,tim,sumclr;

int head[N],cnt[N];

int Stack[N],instack[N],low[N],dfn[N];

struct Edge
{
    int x,y,nxt;
    Edge(int x=0,int y=0,int nxt=0):
        x(x),y(y),nxt(nxt){}
}edge[N];

void add(int x,int y)
{
    edge[++sumedge]=Edge(x,y,head[x]);
    head[x]=sumedge;
}

void Tarjian(int x)
{
    low[x]=dfn[x]=++tim;
    Stack[++top]=x;instack[x]=true;
    for(int i=head[x];i;i=edge[i].nxt)
    {
        int v=edge[i].y;
        if(instack[v]) low[x]=min(low[x],dfn[v]);
        else if(!dfn[v])
        {
            Tarjian(v);
            low[x]=min(low[x],low[v]);
        }
    }
    if(low[x]==dfn[x])
    {
        sumclr++;
        while(Stack[top+1]!=x)
        {
            cnt[sumclr]++;
            instack[Stack[top+1]]=false;
            top--;
        }
    }
}

int main()
{
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
    {
        int x;
        scanf("%d",&x);
        add(i,x);
    }
    for(int i=1;i<=n;i++)
     if(!dfn[i]) Tarjian(i);
    int ans=n+1;
    for(int i=1;i<=sumclr;i++)
     if(cnt[i]!=1) ans=min(ans,cnt[i]);
    cout<<ans<<endl;
    return 0;
}

T3斗地主...

T1跳石头

二分答案

#include<iostream>
#include<cmath>
#include<ctime>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#define LL long long
using namespace std;

int Len,N,M;

int ans;
 
int L,R;

int a[50005]; 

bool check(int x)
{
    int mv,now;mv=now=0;
    for(int i=1;i<=N+1;i++)
    {
        if(a[i]-now<x)mv++;
        else now=a[i];
    }
    return mv<=M;
}
int main()
{
    scanf("%d%d%d",&Len,&N,&M);
    /*
    起点到终点的距离
    起点到终点的岩石数
    至多移走的岩石数 
    */
    for(int i=1;i<=N;i++)scanf("%d",&a[i]);
    a[N+1]=Len;
    L=1;R=Len;
    while(L<=R)
    {
        int mid=(L+R)>>1;
        if(check(mid))ans=mid,L=mid+1;
        else R=mid-1;
    } 
    printf("%d
",ans);
    return 0;
}

T3运输计划

// luogu-judger-enable-o2
#include<iostream>
#include<cmath>
#include<ctime>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#define LL long long
#define N 300005
using namespace std;

int n,m;

int sumedge;

int head[N],s[N],t[N];
LL sum[N];

LL res,ans;

struct E
{
    int x,y,z;
}e[N];

struct Edge
{
    int x,y,z,nxt;
    Edge(int x=0,int y=0,int z=0,int nxt=0):
        x(x),y(y),z(z),nxt(nxt){}
}edge[N<<1];

void add(int x,int y,int z)
{
    edge[++sumedge]=Edge(x,y,z,head[x]);
    head[x]=sumedge;
}

inline int read()
{
    int x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9') {if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}

void dfs(int now,int pre,int ed,int ss,int tt,LL p)
{
    if(now==ed)
    {
        ans=max(ans,p);
        return ;
    }
    for(int i=head[now];i;i=edge[i].nxt)
    {
        int v=edge[i].y;
        if(v==pre) continue;
        if((v==ss&&now==tt)||(v==tt&&now==ss))
        {
            dfs(v,now,ed,ss,tt,p);
        }else dfs(v,now,ed,ss,tt,p+edge[i].z);
    }
}

int main()
{
    n=read();m=read();
    for(int i=1;i<n;i++)
    {
        int x,y,z;
        x=read();y=read();z=read();
        e[i].x=x;e[i].y=y;e[i].z=z;
        sum[y]=sum[x]+z;
        add(x,y,z);
        add(y,x,z);
    }
    for(int i=1;i<=m;i++)
    {
        s[i]=read();t[i]=read();
    }
    if(m==1)
    {
       res=1000000000;
       for(int i=1;i<n;i++)
       {
          ans=0;
          for(int j=1;j<=m;j++)
          {
            dfs(s[j],0,t[j],e[i].x,e[i].y,0);
          }
           res=min(res,ans);
       }
       printf("%lld
",res);
       return 0;
    }
    res=1000000000;
    for(int i=1;i<n;i++)
    {
        int xx,yy;xx=e[i].x;yy=e[i].y;
        if(xx>yy) swap(xx,yy);ans=0;
        for(int j=1;j<=m;j++)
        {
            int xd,yd;xd=s[j];yd=t[j];
            if(xd>yd) swap(xd,yd);
            if(xx>=xd&&yy<=yd)ans=max(ans,sum[yd]-sum[xd]-e[i].z);
            else ans=max(ans,sum[yd]-sum[xd]);
        }
        res=min(res,ans);
    }
    printf("%lld
",res);
    return 0;
}
/*
5 1
1 2 1
2 4 3
2 5 2
1 3 2
3 4
*/