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：
1 #include<cstdio> 2 #include<cstdlib> 3 #include<cmath> 4 #include<cstring> 5 #include<algorithm> 6 #include<iostream> 7 #include<vector> 8 #include<map> 9 #include<set> 10 #include<queue> 11 #include<string> 12 #define inf 1000000000 13 #define maxn 250000 14 #define maxm 500+100 15 #define eps 1e-10 16 #define ll long long 17 #define pa pair<int,int> 18 #define for0(i,n) for(int i=0;i<=(n);i++) 19 #define for1(i,n) for(int i=1;i<=(n);i++) 20 #define for2(i,x,y) for(int i=(x);i<=(y);i++) 21 #define for3(i,x,y) for(int i=(x);i>=(y);i--) 22 #define mod 1000000007 23 using namespace std; 24 inline int read() 25 { 26 int x=0,f=1;char ch=getchar(); 27 while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();} 28 while(ch>='0'&&ch<='9'){x=10*x+ch-'0';ch=getchar();} 29 return x*f; 30 } 31 ll n,tot,a[maxn],b[maxn],c[maxn],d[maxn],s[maxn]; 32 inline bool cmp(int x,int y){return a[x]<a[y];} 33 int main() 34 { 35 //freopen("input.txt","r",stdin); 36 //freopen("output.txt","w",stdout); 37 n=read(); 38 for1(i,n)a[i]=read(),a[n+i]=read(); 39 for1(i,2*n)c[i]=i; 40 sort(c+1,c+2*n+1,cmp); 41 tot=0; 42 for1(i,2*n) 43 { 44 if(i==1||a[c[i]]!=a[c[i-1]])tot++; 45 b[c[i]]=tot;d[tot]=a[c[i]]; 46 } 47 for1(i,n) 48 { 49 s[b[i]]++;s[b[n+i]+1]--; 50 } 51 for1(i,tot)s[i]+=s[i-1]; 52 int ans=0; 53 for1(i,tot)if(s[i]*d[i]>d[ans]*s[ans])ans=i; 54 printf("%lld ",d[ans]*s[ans]); 55 return 0; 56 }