队爷的新书 CH Round #59 - OrzCC杯NOIP模拟赛day1

题目：http://ch.ezoj.tk/contest/CH%20Round%20%2359%20-%20OrzCC杯NOIP模拟赛day1/队爷的新书

题解：看到这题就想到了 poetize 的封印之门，然后就用差分序列水过了。。。不过把线段排序也可以一遍扫出来？

代码：

 #include<cstdio>

 #include<cstdlib>

 #include<cmath>

 #include<cstring>

 #include<algorithm>

 #include<iostream>

 #include<vector>

 #include<map>

 #include<set>

 #include<queue>

 #include<string>

 #define inf 1000000000

 #define maxn 250000

 #define maxm 500+100

 #define eps 1e-10

 #define ll long long

 #define pa pair<int,int>

 #define for0(i,n) for(int i=0;i<=(n);i++)

 #define for1(i,n) for(int i=1;i<=(n);i++)

 #define for2(i,x,y) for(int i=(x);i<=(y);i++)

 #define for3(i,x,y) for(int i=(x);i>=(y);i--)

 #define mod 1000000007

 using namespace std;

 inline int read()

 {

     int x=,f=;char ch=getchar();

     while(ch<''||ch>''){if(ch=='-')f=-;ch=getchar();}

     while(ch>=''&&ch<=''){x=*x+ch-'';ch=getchar();}

     return x*f;

 }

 ll n,tot,a[maxn],b[maxn],c[maxn],d[maxn],s[maxn];

 inline bool cmp(int x,int y){return a[x]<a[y];}

 int main()

 {

     //freopen("input.txt","r",stdin);

     //freopen("output.txt","w",stdout);

     n=read();

     for1(i,n)a[i]=read(),a[n+i]=read();

     for1(i,*n)c[i]=i;

     sort(c+,c+*n+,cmp);

     tot=;

     for1(i,*n)

     {

         if(i==||a[c[i]]!=a[c[i-]])tot++;

         b[c[i]]=tot;d[tot]=a[c[i]];

     }

     for1(i,n)

     {

         s[b[i]]++;s[b[n+i]+]--;

     }

     for1(i,tot)s[i]+=s[i-];

     int ans=;

     for1(i,tot)if(s[i]*d[i]>d[ans]*s[ans])ans=i;

     printf("%lld\n",d[ans]*s[ans]);

     return ;

 }