17/10-17/11做题记录

Posted 2020-10-13 whz2002

1.Luogu P1155 双栈排序

Code:

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 #define inf 0x7fffffff
 5 #define MN 1005
 6 #define ME 1000005
 7 using namespace std;
 8 inline int in(){
 9     int x=0;bool f=0; char c;
10     for (;(c=getchar())<‘0‘||c>‘9‘;f=c==‘-‘);
11     for (x=c-‘0‘;(c=getchar())>=‘0‘&&c<=‘9‘;x=(x<<3)+(x<<1)+c-‘0‘);
12     return f?-x:x;
13 }
14 struct edge{
15     int to,next;
16 }e[ME];
17 int head[MN],col[MN],a[MN],f[MN],st1[MN],st2[MN];
18 int n,cur,c1,c2,cnt=0;
19 inline void ins(int x,int y){
20     e[++cnt].to=y;e[cnt].next=head[x];head[x]=cnt;
21 }
22 inline bool dfs(int u,int c){
23     col[u]=c;
24     for (int i=head[u];i;i=e[i].next){
25         int v=e[i].to;
26         if (col[v]==c) return 0;
27         if (col[v]==-1) dfs(v,c^1);
28     }return 1;
29 }
30 int main()
31 {
32     n=in();f[n+1]=inf;memset(col,-1,sizeof(col));
33     for (int i=1;i<=n;++i) a[i]=in();
34     for (int i=n;i;--i) f[i]=min(a[i],f[i+1]);
35     for (int i=1;i<=n;++i)
36     for (int j=i+1;j<=n;++j){
37         if (a[i]<a[j]&&a[i]>f[j+1]) ins(i,j),ins(j,i);
38     }for (int i=1;i<=n;++i) if(col[i]==-1)
39     if (!dfs(i,0)) {printf("0");return 0;}cur=1;
40     for (int i=1;i<=n;++i){
41         if (!col[i]) st1[++c1]=a[i],printf("a ");
42         else st2[++c2]=a[i],printf("c ");
43         while ((c1&&st1[c1]==cur)||(c2&&st2[c2]==cur)){
44             while (c1&&st1[c1]==cur) printf("b "),--c1,++cur;
45             while (c2&&st2[c2]==cur) printf("d "),--c2,++cur;
46         }
47     }return 0;
48 }

2.Luogu P1099 树网的核

Code:

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 #define inf 0x3f3f3f3f
 5 #define ME 605
 6 #define MN 303
 7 using namespace std;
 8 inline int in(){
 9     int x=0;bool f=0; char c;
10     for (;(c=getchar())<‘0‘||c>‘9‘;f=c==‘-‘);
11     for (x=c-‘0‘;(c=getchar())>=‘0‘&&c<=‘9‘;x=(x<<3)+(x<<1)+c-‘0‘);
12     return f?-x:x;
13 }
14 struct edge{
15     int to,next,val;
16 }e[ME];
17 int head[MN],dis[MN][MN],st[MN];
18 int n,m,s,t,dmx=0,md=inf,res=inf,mx=0,dx,dy,cnt=0,v,ct=0;
19 bool vis[MN],mk=0;
20 inline void ins(int x,int y,int v){
21     e[++cnt].to=y;e[cnt].next=head[x];head[x]=cnt;e[cnt].val=v;
22     dis[x][y]=v;
23 }
24 inline void dfs(int u){
25     if (u==dy) {mk=1;return;}
26     for (int i=head[u];i;i=e[i].next){
27         int v=e[i].to;
28         if (!vis[v]){
29             vis[v]=1;st[++ct]=v;dfs(v);
30             if (mk) return;--ct;
31         }
32     }
33 }
34 
35 int main()
36 {
37     n=in();m=in();
38     memset(dis,0x3f,sizeof(dis));
39     for (int i=1;i<=n;++i) dis[i][i]=0;
40     for (int i=1;i<n;++i){
41         s=in();t=in();v=in();
42         ins(s,t,v);ins(t,s,v);
43     }
44     for (int k=1;k<=n;++k)
45     for (int i=1;i<=n;++i)
46     for (int j=1;j<=n;++j)
47     dis[i][j]=min(dis[i][j],dis[i][k]+dis[k][j]);
48     for (int i=1;i<=n;++i)
49     for (int j=i+1;j<=n;++j){
50         if (dmx<dis[i][j]) dmx=dis[i][j],dx=i,dy=j;
51     }vis[dx]=1,st[++ct]=dx;dfs(dx);memset(vis,0,sizeof(vis));
52     for(int i=1;i<=ct;++i)
53     for(int j=i;j<=ct;++j){
54         int sum=dis[st[i]][st[j]],mx=0;if (sum>m) break;
55         for (int k=1;k<=n;++k){
56             md=inf;for (int l=i;l<=j;++l)
57             md=min(md,dis[k][st[l]]);mx=max(mx,md);
58         }res=min(res,mx?mx:inf);
59     }printf("%d",res);return 0;
60 }

<not_completed>