[NOIP1999] 普及组

回文数

 /*By SilverN*/
 #include<algorithm>
 #include<iostream>
 #include<cstring>
 #include<cstdio>
 #include<cmath>
 using namespace std;
 int read(){
     int x=,f=;char ch=getchar();
     while(ch<'' || ch>''){if(ch=='-')f=-;ch=getchar();}
     while(ch>='' && ch<=''){x=x*+ch-'';ch=getchar();}
     return x*f;
 }
 int m;
 char n[];
 struct number{
     int a[];
     int len;
 }a,b;
 number operator + (number a,number b){
     int len=max(a.len,b.len);
     number c={};c.len=len;
     int tmp=;
     for(int i=;i<=len+;i++){
         c.a[i]=a.a[i]+b.a[i]+tmp;
         tmp=c.a[i]/m;
         c.a[i]%=m;
     }
     if(c.a[c.len+])c.len++;
     return c;
 }
 bool pd(number x){
     for(int i=;i<=x.len/;i++){
         if(x.a[i]!=x.a[x.len-i+])return ;
     }
     return ;
 }
 int main(){
     int step=;
     scanf("%d",&m);
     scanf("%s",n);
     int i,j;
     int slen=strlen(n);
     for(i=;i<slen;i++){
         a.len=i+;
         if(n[slen-i-]>='' && n[slen-i-]<='')
             a.a[i+]=n[slen-i-]-'';
         else a.a[i+]=n[slen-i-]-'A'+;
     }
     while(step<=){
         if(pd(a)){
             printf("STEP=%d\n",step);
             return ;
         }
         number b={};
         b.len=a.len;
         for(i=;i<=b.len;i++)
             b.a[i]=a.a[a.len-i+];
         a=a+b;
         step++;
     }
     printf("Impossible!\n");
     return ;
 }

回文数

导弹拦截

数据范围太小了，所以偷了懒，各种优化都没加

 /*by SilverN*/
 #include<algorithm>
 #include<iostream>
 #include<cstring>
 #include<cstdio>
 #include<cmath>
 using namespace std;
 const int mxn=;
 int h[mxn];
 int ans=;
 int f[mxn],cnt;
 int n=;
 int main(){
     while(scanf("%d",&h[n+])!=EOF ) ++n;
     int i,j;
     for(i=;i<=n;i++)f[i]=;
     for(i=;i<=n;i++)
         for(j=;j<i;j++)
             if(h[j]>=h[i])f[i]=max(f[i],f[j]+);
     ans=;
     for(i=;i<=n;i++) ans=max(ans,f[i]);
     printf("%d\n",ans);
     //part 2
     ans=cnt=;
     memset(f,,sizeof f);
     for(i=;i<=n;i++){
         int mini=0x3f3f3f3f,pos=;
         for(j=;j<=cnt;j++){
             if(f[j]>h[i] && f[j]<mini){
                 mini=f[j];
                 pos=j;
             }
         }
         if(!pos){f[++cnt]=h[i];continue;}
         f[pos]=h[i];
     }
     printf("%d\n",cnt);
     return ;
 }

导弹拦截

邮票面值设计

DP+搜索 这思路挺神的

 /*by SilverN*/
 #include<algorithm>
 #include<iostream>
 #include<cstring>
 #include<cstdio>
 #include<cmath>
 #include<map>
 using namespace std;
 const int mxn=;
 int m,k;
 int a[mxn],cnt=;
 bool vis[mxn];
 int f[mxn];
 int mxans=;
 int ans[mxn];
 int DFS(int pos){
     memset(f,,sizeof f);
     int i,j;
     for(i=;i<=;i++){
         f[i]=0x3f3f3f3f;
         for(j=;j<=pos;j++){
             if(a[j]>i)continue;
             f[i]=min(f[i],f[i-a[j]]+);
         }
         if(f[i]>m)return i;
     }
 }
 void dp(int pos){
     int tmp=DFS(pos);
 //    printf("tmp:%d  pos:%d\n",tmp,pos);
     if(tmp>mxans){
         mxans=tmp;
         cnt=pos;
         memcpy(ans,a,sizeof ans);
     }
     if(pos==k)return;
     for(int i=tmp;i>a[pos];i--){
         a[pos+]=i;
         dp(pos+);
     }
     return;
 }
 int main(){
     scanf("%d%d",&m,&k);
     int i,j;
     a[]=;cnt=;
     dp(cnt);
     for(i=;i<=cnt;i++){
         printf("%d ",ans[i]);
     }
     printf("\nMAX=%d\n",mxans-);
     return ;
 }

邮票面值设计