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 ;
 }