P1052 [NOIP2005 提高组] 过河

JIsoo

关键在于压缩长度

不会证明怎么办

感性理解开个大数\(s*t*10\)

#include<cstdio>
#include<iostream>
#include<cstring>
#include<iomanip>
#include<cmath>
#include<algorithm>
using namespace std;
template<class T>inline void read(T &x)
{
    x=0;register char c=getchar();register bool f=0;
    while(!isdigit(c))f^=c=='-',c=getchar();
    while(isdigit(c))x=(x<<3)+(x<<1)+(c^48),c=getchar();
    if(f)x=-x;
}
template<class T>inline void print(T x)
{
    if(x<0)putchar('-'),x=-x;
    if(x>9)print(x/10);
    putchar('0'+x%10);
}
int l;
int s,t,m;
int f[3000000];
int dis;
int ans;
int nd[3000000];
int a[3000000]; 
int main(){
	read(l);
	read(s);read(t);read(m);
	for(int i=1;i<=m;++i){
		read(a[i]);
	} 
	sort(a+1,a+m+1);
	a[m+1]=l;
	m++;
	if(s==t){
		int cnt=0; 
		for(int i=1;i<=m;++i){
			if(a[i]%s==0){
				cnt++;
			}
		}
		cout<<cnt;
		return 0;
	}else{
		for(int i=1;i<=m;++i){
			dis+=min(a[i]-a[i-1],s*t*10);
			nd[dis]=1;
		}
		nd[dis]=0;
		memset(f,0x3f,sizeof(f));
		f[0]=0;
		for(int i=1;i<=dis+9;++i){
			for(int j=s;j<=t;++j){
				if(i-j<0) continue;
				f[i]=min(f[i],f[i-j]);
			}
			f[i]+=nd[i];
		}
		int cnt=99999999999;
		for(int i=0;i<=9;++i){
			cnt=min(cnt,f[i+dis]);
		}
		cout<<cnt;
	}
	return 0;
}