[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=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;
char n[120];
struct number{
    int a[300];
    int len;
}a,b;
number operator + (number a,number b){
    int len=max(a.len,b.len);
    number c={0};c.len=len;
    int tmp=0;
    for(int i=1;i<=len+1;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+1])c.len++;
    return c;
}
bool pd(number x){
    for(int i=1;i<=x.len/2;i++){
        if(x.a[i]!=x.a[x.len-i+1])return 0;
    }
    return 1;
}
int main(){
    int step=0;
    scanf("%d",&m);
    scanf("%s",n);
    int i,j;
    int slen=strlen(n);
    for(i=0;i<slen;i++){
        a.len=i+1;
        if(n[slen-i-1]>='0' && n[slen-i-1]<='9')
            a.a[i+1]=n[slen-i-1]-'0';
        else a.a[i+1]=n[slen-i-1]-'A'+10;
    }
    while(step<=30){
        if(pd(a)){
            printf("STEP=%d\n",step);
            return 0;
        }
        number b={0};
        b.len=a.len;
        for(i=1;i<=b.len;i++)
            b.a[i]=a.a[a.len-i+1];
        a=a+b;
        step++;
    }
    printf("Impossible!\n");
    return 0;
}

 

 

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=200;
int h[mxn];
int ans=0;
int f[mxn],cnt;
int n=0;
int main(){
    while(scanf("%d",&h[n+1])!=EOF ) ++n;
    int i,j;
    for(i=1;i<=n;i++)f[i]=1;
    for(i=1;i<=n;i++)
        for(j=1;j<i;j++)
            if(h[j]>=h[i])f[i]=max(f[i],f[j]+1);
    ans=0;
    for(i=1;i<=n;i++) ans=max(ans,f[i]);
    printf("%d\n",ans);
    //part 2
    ans=cnt=0;
    memset(f,0,sizeof f);
    for(i=1;i<=n;i++){
        int mini=0x3f3f3f3f,pos=0;
        for(j=1;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 0;
}

 

 

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=1000;
int m,k;
int a[mxn],cnt=0;
bool vis[mxn];
int f[mxn];
int mxans=0;
int ans[mxn];
int DFS(int pos){
    memset(f,0,sizeof f);
    int i,j;
    for(i=1;i<=2000;i++){
        f[i]=0x3f3f3f3f;
        for(j=1;j<=pos;j++){
            if(a[j]>i)continue;
            f[i]=min(f[i],f[i-a[j]]+1);
        }
        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+1]=i;
        dp(pos+1);
    }
    return;
}
int main(){
    scanf("%d%d",&m,&k);
    int i,j;
    a[1]=1;cnt=1;
    dp(cnt);
    for(i=1;i<=cnt;i++){
        printf("%d ",ans[i]);
    }
    printf("\nMAX=%d\n",mxans-1);
    return 0;
}