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NOI2014 动物园
80pts
用倍增暴力跳nxt数组

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#define MAXN 1000010
#define MOD 1000000007
#define ull unsigned long long
using namespace std;
int T,len,ans;
int nxt[MAXN],fp[22][MAXN];
char s[MAXN];
int main()
{
    #ifndef ONLINE_JUDGE
    freopen("ce.in","r",stdin);
    #endif
    scanf("%d",&T);
    while(T--)
    {
        ans=1;
        memset(nxt,0,sizeof(nxt));
        scanf("%s",s+1);
        len=strlen(s+1);
        int p=0;
        for(int i=2;i<=len;i++)
        {
            while(p&&s[p+1]!=s[i]) p=nxt[p];
            if(s[p+1]==s[i]) p++;
            nxt[i]=p;
        }
        for(int i=2;i<=len;i++) fp[0][i]=nxt[i];
        for(int k=1;k<=21;k++)
            for(int i=2;i<=len;i++)
                fp[k][i]=fp[k-1][fp[k-1][i]];
        for(int i=2;i<=len;i++)
        {
            int now=i;
            for(int j=21;j>=0;j--)
                if(fp[j][now]*2>i)
                    now=fp[j][now];
            int cur_ans=0;
            for(int j=21;j>=0;j--)
                if(fp[j][now])
                    cur_ans+=(1<<j),now=fp[j][now];
            ans=1ll*ans*(cur_ans+1)%MOD;
        }
        printf("%d
",ans);
    }
    return 0;
}

NOI2016 优秀的拆分
95pts
hash直接水,(n^2)判断字符串是否相同

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#define MAXN 1000010
#define ull unsigned long long
using namespace std;
int T,n,m;
int base[MAXN],kkk[MAXN];
long long ans;
char s[MAXN];
const int prime=233;
inline void init()
{
    base[0]=1;
    for(int i=1;i<=n;i++)
    {
        base[i]=base[i-1]*prime;
        kkk[i]=kkk[i-1]*prime+s[i]-'a';
    }
}
inline ull query(int l,int r){return kkk[r]-kkk[l-1]*base[r-l+1];}
inline bool check(int l,int r)
{
    if((r-l+1)&1) return false;
    int mid=(l+r)>>1;
    if(query(l,mid)==query(mid+1,r)) return true;
    return false;
}
int main()
{
    #ifndef ONLINE_JUDGE
    freopen("ce.in","r",stdin);
    #endif
    scanf("%d",&T);
    while(T--)
    {
        ans=0;
        scanf("%s",s+1);
        n=strlen(s+1);
        init();
        for(int i=1;i<=n;i++)
        {
            int st=0,en=0;
            for(int j=1;j<=i;j++)
                if(check(j,i)) en++;
            for(int j=i+1;j<=n;j++)
                if(check(i+1,j)) st++;
            ans+=1ll*en*st;
        }
        printf("%lld
",ans);
    }
    return 0;
}

CTS2019 无处安放

前三个可以手算：

//test1
1 0 0 1
1 0 2 1
1 10 0 1
1 18 0 0
1 34 0 1
1 34 2 1
1 26 0 0
1 40 0 1

//test2
1 2 0 1
1 2 5 0
1 10 5 1
1 13 3 0
1 16 8 0
1 13 7 1
1 16 7 0
1 0 0 0
1 6 7 1
1 6 0 0
1 13 0 1
1 10 0 1

//test3
1 0 5 1
1 3 5 0
1 5 0 0
1 9 9 0
1 5 5 0
1 10 4 1
1 0 0 0
1 5 8 0
1 8 3 1
1 12 6 1
1 3 8 0
1 6 5 0
1 5 3 1
1 12 3 1
1 6 8 1
1 9 4 0

//test4贪心代码
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<vector>
#define MAXN 100010
using namespace std;
int type,k,n,m;
bool done[MAXN];
vector<int>vec;
struct Node{int id,x,y,ansx,ansy,op,dir;}node[MAXN];
inline bool cmp1(struct Node a,struct Node b)
{
    if(a.y==b.y) return a.x>b.x;
    return a.y>b.y;
}
inline bool cmp2(struct Node a,struct Node b){return a.id<b.id;}
int main()
{
    freopen("nowhere4.in","r",stdin);
    freopen("nowhere4.out","w",stdout);
    scanf("%d%d",&type,&k);
    scanf("%d%d",&n,&m); 
    for(int i=1;i<=k;i++)
    {
        scanf("%d%d",&node[i].x,&node[i].y);
        if(node[i].x>node[i].y) swap(node[i].x,node[i].y),node[i].dir=1;
        node[i].id=i;
    }
    int now=0;
    sort(&node[1],&node[k+1],cmp1);
    // for(int i=1;i<=100;i++) printf("%d %d
",node[i].x,node[i].y);
    for(int i=1;i<=k;i++)
    {
        if(node[i].y!=4) break;
        done[i]=1;
        node[i].op=1;
        node[i].ansx=now,node[i].ansy=0;
        now+=node[i].x;
        if(node[i].x==4&&node[i].y==4) vec.push_back(i);
    }
    // cout<<now<<endl;
    int cur1=now,cur2=now,cnt=0;
    for(int i=1;i<=k;i++)
    {
        if(node[i].x==3&&node[i].y==3)
        {                                                
            done[i]=1;
            node[i].op=1;
            node[i].ansx=cur1,node[i].ansy=0;
            cur1+=node[i].x;
            cnt++;
            if(cnt==448) break;
        }
    }
    // printf("cur1=%d
",cur1);
    cnt=0;
    for(int i=1;i<=k;i++)
    {
        if(node[i].x==1&&node[i].y==3)
        {
            done[i]=1;
            node[i].op=1;
            node[i].ansx=cur2,node[i].ansy=3;
            cur2+=node[i].y;
            node[i].dir=1;
            cnt++;
            if(cnt==448) break;
        }
    }
    // printf("cur2=%d
",cur2);
    now=cur1;
    cur1=now,cur2=now;int cur3=now;
    cnt=0;
    for(int i=1;i<=k;i++)
    {
        if(node[i].x==3&&node[i].y==3&&done[i]==0)
        {
            done[i]=1;
            node[i].op=1;
            node[i].ansx=cur1,node[i].ansy=0;
            cur1+=node[i].x;
            cnt++;
            if(cnt==350) break;
        }
    }
    cnt=0;
    // printf("cur1=%d
",cur1);
    for(int i=1;i<=k;i++)
    {
        if(node[i].x==1&&node[i].y==1&&done[i]==0)
        {
            done[i]=1;
            node[i].op=1;
            node[i].ansx=cur2,node[i].ansy=3;
            cur2+=3;
            cnt++;
            if(cnt==350) break;
        }
    }
    cnt=0;
    // printf("cur2=%d
",cur2);
    for(int i=1;i<=k;i++)
    {
        if(node[i].x==1&&node[i].y==2&&done[i]==0)
        {
            done[i]=1;
            node[i].op=1;
            node[i].ansx=cur3+1,node[i].ansy=3;
            node[i].dir=1;
            cur3+=3;
            cnt++;
            if(cnt==350) break;
        }
    }
    now=cur1;
    cur1=now,cur2=0;
    for(int i=1;i<=k;i++)
    {
        if(node[i].x==2&&node[i].y==3&&done[i]==0)
        {
            done[i]=1;
            node[i].op=1;
            node[i].ansx=cur1,node[i].ansy=(cur2==0?0:2);
            node[i].dir=1;
            if(cur2==1)cur1+=3;
            cur2^=1;
        }
    }
    now=cur1,cur1=now,cur2=0;
    for(int i=1;i<=k;i++)
    {
        if(node[i].x==2&&node[i].y==2&&done[i]==0)
        {
            done[i]=1;
            node[i].op=1;
            node[i].ansx=cur1,node[i].ansy=(cur2==0?0:2);
            if(cur2==1)cur1+=2;
            cur2^=1;
        }
    }
    for(int i=1;i<=k;i++)
    {
        if(node[i].x==1&&node[i].y==2&&done[i]==0)
        {
            done[i]=1;
            node[i].op=1;
            node[i].ansx=cur1,node[i].ansy=2;
            node[i].dir=1;
            break;
        }
    }
    for(int i=1;i<=k;i++)
    {
        if(node[i].x==1&&node[i].y==2&&done[i]==0)
        {
            done[i]=1;
            node[i].op=1;
            node[i].ansx=cur1,node[i].ansy=3;
            node[i].dir=1;
            break;
        }
    }
    now=cur1+2;
    cur1=now,cur2=0;
    for(int i=1;i<=k;i++)
    {
        if(node[i].x==1&&node[i].y==2&&done[i]==0)
        {
            done[i]=1;
            node[i].op=1;
            node[i].ansx=cur1,node[i].ansy=(cur2==0?0:2);
            if(cur2==1)cur1+=1;
            cur2^=1;
        }
    }
    now=cur1;
    // cout<<now<<endl;
    for(int i=1;i<=k;i++)
    {
        if(node[i].x==1&&node[i].y==1&&done[i]==0)
        {
            done[i]=1;
            node[i].op=1;
            node[i].ansx=cur1,node[i].ansy=2;
            node[i].dir=1;
            break;
        }
    }
    for(int i=1;i<=k;i++)
    {
        if(node[i].x==1&&node[i].y==1&&done[i]==0)
        {
            done[i]=1;
            node[i].op=1;
            node[i].ansx=cur1,node[i].ansy=3;
            node[i].dir=1;
            break;
        }
    }
    now=cur1+1;
    cur1=now,cur2=0;
    // cout<<now<<endl;
    for(int i=1;i<=k;i++)
    {
        if(node[i].x==1&&node[i].y==1&&done[i]==0)
        {
            // cout<<i<<endl;
            done[i]=1;
            node[i].op=1;
            node[i].ansx=cur1;
            node[i].ansy=cur2;
            cur2++;
            if(cur2==4)cur1++;
            if(cur1>=7518) break;
            cur2%=4;
        }
    }
    cur1=0,cur2=0,cur3=0,cnt=0;
    node[vec[0]].op=node[vec[1]].op=node[vec[2]].op=0;
    for(int i=1;i<=k;i++)
    {
        if(done[i]==0&&node[i].x==1&&node[i].y==1)
        {
            done[i]=1;
            node[i].op=1;
            node[i].ansx=cur2,node[i].ansy=cur3;
            cur3++;
            if(cur3==4)cur2++,cur3=0;
        }
    }
    // for(int i=1;i<=k;i++)
    // {
    //     if(node[i].op==0)
    //         printf("%d %d
",node[i].x,node[i].y);
    // }
    sort(&node[1],&node[k+1],cmp2);
    for(int i=1;i<=k;i++)
    {
        // if(node[i].x==1&&node[i].y==3)
        if(node[i].op==0) printf("0
");
        else printf("%d %d %d %d
",node[i].op,node[i].ansx,node[i].ansy,node[i].dir);
    }
    return 0;
}

CTS2019 珍珠

#include<iostream>
#include<cmath>
#include<cstring>
#include<cstdio>
#include<algorithm>
#define MAXN 4010
#define mod 998244353
using namespace std;
int d,n,m,ans;
int dp[MAXN][MAXN];
inline int fpow(int x,int y)
{
	int cur_ans=1;
	while(y)
	{
		if(y&1) cur_ans=1ll*cur_ans*x%mod;
		x=1ll*x*x%mod;
		y>>=1;
	}
	return cur_ans;
}
int main()
{
	#ifndef ONLINE_JUDGE
	freopen("ce.in","r",stdin);
	#endif
	scanf("%d%d%d",&d,&n,&m);
	if(m<=1)
	{
		printf("%d
",fpow(d,n)%mod);
		return 0;
	}
	dp[0][0]=1;
	for(int i=0;i<n;i++)
		for(int j=0;j<=d;j++)
		{
			if(j+1<=d) dp[i+1][j+1]=(dp[i+1][j+1]+1ll*dp[i][j]*(d-j)%mod)%mod;
			if(j-1>=0) dp[i+1][j-1]=(dp[i+1][j-1]+1ll*dp[i][j]*j%mod)%mod;
		}
	for(int i=0;i<=d;i++)
	{
		if(n-i>=2*m)
			ans=(ans+dp[n][i])%mod;
	}
	printf("%d
",ans);
	return 0;
}

NOI2016 国王饮水记
53pts

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<vector>
#define MAXN 100010
using namespace std;
int n,k,p;
double a[MAXN],tmp[MAXN];
inline bool cmp(int x,int y){return x>y;}
namespace subtask1
{
    inline void solve()
    {
        double cur_ans=a[1],ans=0;
        double cur=a[1];
        sort(&a[1],&a[n+1],cmp);
        for(int i=1;i<=n;i++)
        {
            if(a[i]==cur) break;
            cur_ans+=a[i];
            ans=max(ans,cur_ans/(i+1));
        }
        printf("%lf
",ans);
    }
}
namespace subtask2
{
    inline void solve()
    {
        double cur_ans=a[1],ans=0;
        double cur=a[1];
        sort(&a[1],&a[n+1]);
        int i;
        for(i=1;i<=n;i++)
            if(a[i]==cur) break;
        // printf("i=%d
",i);
        while(i<=n)
        {
            if(a[i]<a[1]) continue;
            a[1]=(a[1]+a[i])/2;
            i++;
        }
        printf("%lf
",a[1]);
    }
}
namespace subtask3
{
    inline void solve()
    {
        vector<double>vec;
        for(int i=2;i<=n;i++)
            if(a[i]>a[1])
                vec.push_back(a[i]);
        sort(vec.begin(),vec.end());
        for(int i=vec.size()-k;i<vec.size();i++)
            if(vec[i]>a[1])
                a[1]=(a[1]+vec[i])/2;
        printf("%lf
",a[1]);
    }
}
int main()
{
    #ifndef ONLINE_JUDGE
    freopen("ce.in","r",stdin);
    // freopen("ce.out","w",stdout);
    #endif
    int cnt=0;
    scanf("%d%d%d",&n,&k,&p);
    for(int i=1;i<=n;i++) scanf("%lf",&a[i]);
    for(int i=2;i<=n;i++)
        if(a[i]>a[1])
            cnt++;
    if(k==1) subtask1::solve();
    else if(k>=cnt) subtask2::solve();
    else subtask3::solve();
    return 0;
}

根据dfs序生成树：

inline void dfs(int cur)
{
    if(cur>=n){return;}
    int x=a1[cur],y=a1[cur+1],z=fa[x];
    fa[y]=x;
    e[x].push_back(y);
    dfs(cur+1);
    e[x].pop_back();
    for(;z;z=fa[z])
    {
        fa[y]=z;
        e[z].push_back(y);
        dfs(cur+1);
        e[z].pop_back();
    }
}