72 lines
2.7 KiB
C++
72 lines
2.7 KiB
C++
#include<cstdio>
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struct char_reader
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{
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FILE* f; char *buf,*p1,*p2; int size;
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char_reader(FILE* fin,int bufsize=1000000) { f=fin; size=bufsize; p1=p2=0; buf=new char[bufsize]; }
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inline int operator()() { return p1==p2&&(p2=(p1=buf)+fread(buf,1,size,f),p1==p2)?EOF:*p1++; }
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};
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struct char_writer
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{
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FILE* f; char *buf,*p,*end;
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char_writer(FILE* fout,int bufsize=1000000) { f=fout; buf=new char[bufsize]; p=buf; end=buf+bufsize; }
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~char_writer() { fwrite(buf,p-buf,1,f); }
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inline char operator()(char ch) { return end==p&&(fwrite(buf,end-buf,1,f),p=buf),*p++=ch; }
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};
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char_reader gch(stdin);
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char_writer wch(stdout);
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template<typename T> inline void read(T& t)
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{
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t=0; bool f=false; char ch;
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while(ch=gch(),!((ch>='0'&&ch<='9')||ch=='-'));
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if(ch=='-') f=true,ch=gch();
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t=ch-'0';
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while(ch=gch(),ch>='0'&&ch<='9') t=t*10+ch-'0';
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if(f) t=-t;
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}
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template<typename T> inline void write(T t)
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{
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int stk[20],cnt=0;
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if(t==0) { wch('0'); return; }
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if(t<0) { wch('-'); t=-t; }
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while(t>0) { stk[cnt++]=t%10; t/=10; }
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while(cnt) wch(stk[--cnt]+'0');
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}
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inline void write(char t) { wch(t); }
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inline void write(const char *&s) { while(*s) wch(*s++); }
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#if __cplusplus >= 201103L
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template<typename T,typename... Args> inline void read(T& t,Args&... args) { read(t); read(args...); }
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template<typename T,typename... Args> inline void write(T t,Args... args) { write(t); write(args...); }
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#else
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template<typename A_t,typename B_t> inline void read(A_t &a,B_t &b) { read(a); read(b); }
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template<typename A_t,typename B_t,typename C_t> inline void read(A_t &a,B_t &b,C_t &c) { read(a); read(b); read(c); }
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template<typename A_t,typename B_t,typename C_t,typename D_t> inline void read(A_t &a,B_t &b,C_t &c,D_t &d) { read(a); read(b); read(c); read(d); }
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template<typename A_t,typename B_t> inline void write(A_t a,B_t b) { write(a); write(b); }
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template<typename A_t,typename B_t,typename C_t> inline void write(A_t a,B_t b,C_t c) { write(a); write(b); write(c); }
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template<typename A_t,typename B_t,typename C_t,typename D_t> inline void write(A_t a,B_t b,C_t c,D_t d) { write(a); write(b); write(c); write(d); }
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#endif
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#include<cstring>
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#include<algorithm>
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using namespace std;
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typedef long long LL;
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const int maxn=300005;
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int n,s,q[maxn],l,r;
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LL f[maxn],ST[maxn],SC[maxn];
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int main()
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{
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#ifdef local
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freopen("pro.in","r",stdin);
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#endif
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read(n,s);
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for(int i=1;i<=n;i++) { read(ST[i]); read(SC[i]); ST[i]+=ST[i-1]; SC[i]+=SC[i-1]; }
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memset(f,0x3f,sizeof(f));
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f[0]=0; l=1; r=1; q[1]=0;
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for(int i=1;i<=n;i++)
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{
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while(l<r&&(f[q[l+1]]-f[q[l]])<=(s+ST[i])*(SC[q[l+1]]-SC[q[l]])) l++;
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f[i]=f[q[l]]-(s+ST[i])*SC[q[l]]+ST[i]*SC[i]+s*SC[n];
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while(l<r&&(f[q[r]]-f[q[r-1]])*(SC[i]-SC[q[r]])>=(f[i]-f[q[r]])*(SC[q[r]]-SC[q[r-1]])) r--;
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q[++r]=i;
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}
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write(f[n],'\n');
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return 0;
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} |