Submission #951076

#	Time	Username	Problem	Language	Result	Execution time	Memory
951076		sleepntsheep	Aliens (IOI16_aliens)	C11	100 / 100	201 ms	8372 KiB

aliens

unsigned X=12345;
int rand_(){return(X*=3)>>1;}
long long hi(long long a,long long b){return a>b?a:b;}
int(*compar)(int,int);
void sort_(int*aa,int l,int r)
{
    while(l<r)
    {
        int i=l,j=l,k=r,t,p=aa[l+rand_()%(r-l)];
        while(j<k)
            switch(compar(aa[j],p))
            {
                case 0:++j;break;
                case -1:t=aa[i],aa[i]=aa[j],aa[j]=t,++i,++j;break;
                case 1:t=aa[--k],aa[k]=aa[j],aa[j]=t;break;
            }
        sort_(aa,l,i);
        l=k;
    }
}

#include "aliens_c.h"
#include<string.h>
long long lo(long long a,long long b){return a<b?a:b;}

typedef struct { long long m, c, i; } line;

#define N 100001
int n,m,k,r[N],c[N],*r0,*c0;
long long ans;

int comparpoint0(int i,int j)
{
    if(r0[i]==r0[j])return c0[i]>c0[j]?-1:c0[i]<c0[j]?1:0;
    return r0[i]<r0[j]?-1:r0[i]>r0[j]?1:0;
}

void filter_covered()
{
    int real_n=0,last_noncvered=-1;
    static int o[100002]={0};
    for(int i=0;i<n;++i)o[i]=i;
    compar=comparpoint0;
    sort_(o,0,n);
    for(int i=0;i<n;++i)
    {
        int j=o[i],cver=last_noncvered>=c0[j];
        if(!cver) ++real_n,r[real_n]=r0[j],c[real_n]=c0[j],last_noncvered=c0[j];
    }
    n=real_n;
}

line cht[N<<1];
int head,tail;

double intersectx(line a,line b) { return (b.c-a.c)*1.0L/(a.m-b.m); }

void chtadd(line k)
{
    while(head-tail>1&&intersectx(k,cht[head-1])<intersectx(cht[head-1],cht[head-2]))--head;
    cht[head++]=k;
}

line chtqry(long long x)
{
    while(head-tail>1&&intersectx(cht[tail],cht[tail+1])<x)++tail;
    return cht[tail];
}


#define ASSERT(x) if (!(x)) __builtin_trap()

long long sq(long long x){ return x*x;}

long long what(long long lambda,int*count)
{
    head=tail=0;
    static long long dp[N];
    static int use[N]={0};
    dp[0]=0;
    use[0]=0;

    for(int i=1;i<=n;++i)
    {
        long long L=r[i]-1;
        long long intersect = i>1 ? sq(hi(0,c[i-1]-L)) : 0;

        chtadd((line){-2*L,L*L+lambda+dp[i-1] - intersect, i-1});

        line best=chtqry(c[i]);
        dp[i]=best.m*c[i]+best.c+1ll*c[i]*c[i];

        use[i]=use[best.i]+1;
    }

    *count=use[n];
    return dp[n];
}

long long take_photos(int n0, int m0, int k0, int* r00, int* c00)
{
    n=n0,m=m0,k=k0;
    /* preprocess point - turn to 1-indexed, turn to right diagonal */
    for(int i=0;i<n;++i)
    {
        ++r00[i],++c00[i];
        if(r00[i]>c00[i]){int tt=r00[i];r00[i]=c00[i];c00[i]=tt;}
    }
    r0=r00,c0=c00;
    filter_covered();
    if(k>n)k=n;

    int count;
    long long l=0,r=1e15;
    while(l<=r)
    {
        long long o=l+(r-l)/2;
        what(o,&count);
        if(count>k) l=o+1;
        else r=o-1;
    }
    ans=what(r+1,&count);

    return ans - k*(r+1ll);
}

• Subtask 1: 4 / 4
• Subtask 2: 12 / 12
• Subtask 3: 9 / 9
• Subtask 4: 16 / 16
• Subtask 5: 19 / 19
• Subtask 6: 40 / 40