NOIP2017普及组

A.。。。
B.枚举
C.建图spfa。
D.二分答案+dp+单调队列优化。

A

#include <bits/stdc++.h>using namespace std;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;}int main(){    int a=read(),b=read(),c=read();    printf("%d\n",a/10*2+b/10*3+c/10*5);    return 0;}

B

#include <bits/stdc++.h>using namespace std;#define ll long long#define inf 0x3f3f3f3f#define N 1100inline 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;}int n,q,a[N],bin[10];int main(){//  freopen("a.in","r",stdin);    n=read();q=read();bin[0]=1;    for(int i=1;i<=n;++i) a[i]=read();sort(a+1,a+n+1);    for(int i=1;i<=8;++i) bin[i]=bin[i-1]*10;    while(q--){        int y=read(),x=read(),ans=0;        for(int i=1;i<=n;++i) if(a[i]%bin[y]==x){ans=i;break;}        if(!ans) puts("-1");        else printf("%d\n",a[ans]);    }return 0;}

C

#include <bits/stdc++.h>using namespace std;#define ll long long#define inf 0x3f3f3f3f#define M 110#define N 30000inline 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;}int m,n,mp[M][M],h[N],num=0,dx[]={0,0,1,-1},dy[]={1,-1,0,0},dis[N];bool inq[N];struct edge{    int to,next,val;}data[N<<2];inline void add(int x,int y,int val){    data[++num].to=y;data[num].next=h[x];h[x]=num;data[num].val=val;}void spfa(){    queue<int>q;memset(inq,0,sizeof(inq));memset(dis,inf,sizeof(dis));    q.push(2);dis[2]=0;inq[2]=1;    while(!q.empty()){        int x=q.front();q.pop();inq[x]=0;        for(int i=h[x];i;i=data[i].next){            int y=data[i].to;            if(dis[y]>dis[x]+data[i].val){                dis[y]=dis[x]+data[i].val;                if(!inq[y]) q.push(y),inq[y]=1;            }        }    }}int main(){//  freopen("a.in","r",stdin);    n=read();m=read();    while(m--){        int x=read(),y=read(),col=read();mp[x][y]=col+1;    }for(int i=1;i<=n;++i)        for(int j=1;j<=n;++j)            for(int k=0;k<4;++k){                int x=i+dx[k],y=j+dy[k];                if(x<1||x>n||y<1||y>n) continue;                if(mp[i][j]&&mp[x][y]) add((i-1)*n+j<<1,(x-1)*n+y<<1,mp[i][j]==mp[x][y]?0:1);                else if(mp[i][j]&&!mp[x][y]){                    add((i-1)*n+j<<1,(x-1)*n+y<<1,mp[i][j]==1?2:3);                    add((i-1)*n+j<<1,((x-1)*n+y<<1)-1,mp[i][j]==2?2:3);                }else if(!mp[i][j]&&mp[x][y]){                    add((i-1)*n+j<<1,(x-1)*n+y<<1,mp[x][y]==1?0:1);                    add(((i-1)*n+j<<1)-1,(x-1)*n+y<<1,mp[x][y]==2?0:1);                }            }spfa();int ans=min(dis[n*n<<1],dis[(n*n<<1)-1]);    if(ans==inf) puts("-1");    else printf("%d\n",ans);    return 0;}

D

#include <bits/stdc++.h>using namespace std;#define ll long long#define inf 0x3f3f3f3f#define N 500010#define pa pair<int,int>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;}int n,d,k,p[N],val[N],dp[N];bool jud(int x){    int a=max(1,d-x),b=d+x,now=-1;memset(dp,0,sizeof(dp));    deque<pa>q;    for(int i=1;i<=n;++i){        while(!q.empty()&&q.front().second<p[i]-b) q.pop_front();        while(now<i&&p[now+1]<p[i]-b) ++now;        while(now<i&&p[now+1]<=p[i]-a){            ++now;if(dp[now]==-inf) continue;            while(!q.empty()&&q.back().first<=dp[now]) q.pop_back();            q.push_back(make_pair(dp[now],p[now]));        }if(q.empty()) dp[i]=-inf;        else dp[i]=q.front().first+val[i];if(dp[i]>=k) return 1;    }return 0;}int main(){//  freopen("testdata.in","r",stdin);    n=read();d=read();k=read();    for(int i=1;i<=n;++i) p[i]=read(),val[i]=read();    int l=0,r=1e9;    while(l<=r){        int mid=l+r>>1;        if(jud(mid)) r=mid-1;        else l=mid+1;    }if(r==1e9) puts("-1");    else printf("%d\n",r+1);    return 0;}

为什么要去写普及组啊？因为提高组我都不会啊。像我这样的蒟蒻只能写一写普及组的题了。要是考场上真写这C，D题，我怕是也得挂了吧。蒟蒻怎么办？多做题吧。