【BZOJ1597】【Usaco2008 Mar】土地购买

斜率优化水题

不开long long简直制杖

// <1597.cpp> - 07/19/16 20:00:09
// This file is created by XuYike's black technology automatically.
// Copyright (C) 2015 ChangJun High School, Inc.
// I don't know what this program is.

#include <iostream>
#include <vector>
#include <algorithm>
 #include <cstring>
#include <cstdio>
#include <cmath>
using namespace std;
typedef long long lol;
int gi(){
    int res=0,fh=1;char ch=getchar();
    while((ch>'9'||ch<'0')&&ch!='-')ch=getchar();
    if(ch=='-')fh=-1,ch=getchar();
    while(ch>='0'&&ch<='9')res=res*10+ch-'0',ch=getchar();
    return fh*res;
}
const int MAXN=50010;
const int INF=1e9;
struct land{
    int x,y;
    bool operator <(const land b) const{return x==b.x?y<b.y:x<b.x;}
}a[MAXN];
lol dp[MAXN];
#define k(u,v) double(dp[v-1]-dp[u-1])/(a[v].y-a[u].y)
int q[MAXN];
bool v[MAXN];
int main(){
    int n=gi();
    for(int i=1;i<=n;i++)a[i].x=gi(),a[i].y=gi();
    sort(a+1,a+n+1);
    int maxy=0;
    for(int i=n;i;i--)
        if(a[i].y>maxy)v[i]=1,maxy=max(maxy,a[i].y);
    int t=0;
    for(int i=1;i<=n;i++)if(v[i])a[++t]=a[i];
    n=t;
    int l=1,r=0;
    for(int i=1;i<=n;i++){
        while(l<r&&k(q[r-1],q[r])<=k(q[r],i))r--;
        q[++r]=i;
        while(l<r&&k(q[l],q[l+1])>=-a[i].x)l++;
        dp[i]=dp[q[l]-1]+1ll*a[i].x*a[q[l]].y;
    }
    printf("%lld",dp[n]);
    return 0;
}

// <1597.cpp> - 07/19/16 20:00:09

// This file is created by XuYike's black technology automatically.

// I don't know what this program is.

#include <iostream>

#include <vector>

#include <algorithm>

#include <cstring>

#include <cstdio>

#include <cmath>

using namespace std;

typedef long long lol;

int gi(){

int res=0,fh=1;char ch=getchar();

while((ch>'9'||ch<'0')&&ch!='-')ch=getchar();

if(ch=='-')fh=-1,ch=getchar();

while(ch>='0'&&ch<='9')res=res*10+ch-'0',ch=getchar();

return fh*res;

}

const int MAXN=50010;

const int INF=1e9;

struct land{

int x,y;

bool operator <(const land b) const{return x==b.x?y<b.y:x<b.x;}

}a[MAXN];

lol dp[MAXN];

#define k(u,v) double(dp[v-1]-dp[u-1])/(a[v].y-a[u].y)

int q[MAXN];

bool v[MAXN];

int main(){

int n=gi();

for(int i=1;i<=n;i++)a[i].x=gi(),a[i].y=gi();

sort(a+1,a+n+1);

int maxy=0;

for(int i=n;i;i--)

if(a[i].y>maxy)v[i]=1,maxy=max(maxy,a[i].y);

int t=0;

for(int i=1;i<=n;i++)if(v[i])a[++t]=a[i];

n=t;

int l=1,r=0;

for(int i=1;i<=n;i++){

while(l<r&&k(q[r-1],q[r])<=k(q[r],i))r--;

q[++r]=i;

while(l<r&&k(q[l],q[l+1])>=-a[i].x)l++;

dp[i]=dp[q[l]-1]+1ll*a[i].x*a[q[l]].y;

}

printf("%lld",dp[n]);

return 0;

}

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