BZOJ2348: [Baltic 2011]Plagiarism

 1 #include<cstdio>
 2 
 3 #include<cstdlib>
 4 
 5 #include<cmath>
 6 
 7 #include<cstring>
 8 
 9 #include<algorithm>
10 
11 #include<iostream>
12 
13 #include<vector>
14 
15 #include<map>
16 
17 #include<set>
18 
19 #include<queue>
20 
21 #include<string>
22 
23 #define inf 1000000000
24 
25 #define maxn 100000+5
26 
27 #define maxm 20000000+5
28 
29 #define eps 1e-10
30 
31 #define ll long long
32 
33 #define pa pair<int,int>
34 
35 #define for0(i,n) for(int i=0;i<=(n);i++)
36 
37 #define for1(i,n) for(int i=1;i<=(n);i++)
38 
39 #define for2(i,x,y) for(int i=(x);i<=(y);i++)
40 
41 #define for3(i,x,y) for(int i=(x);i>=(y);i--)
42 
43 #define mod 1000000007
44 
45 using namespace std;
46 
47 inline int read()
48 
49 {
50 
51     int x=0,f=1;char ch=getchar();
52 
53     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
54 
55     while(ch>=‘0‘&&ch<=‘9‘){x=10*x+ch-‘0‘;ch=getchar();}
56 
57     return x*f;
58 
59 }
60 int n,a[maxn];
61 
62 int main()
63 
64 {
65 
66     freopen("input.txt","r",stdin);
67 
68     freopen("output.txt","w",stdout);
69 
70     n=read();
71     for1(i,n)a[i]=read();
72     sort(a+1,a+n+1);ll ans=0;
73     for1(i,n)
74     {
75         int l=i+1,r=n;
76         while(l<=r)
77         {
78             int mid=(l+r)>>1;
79             if(10*a[i]>=9*a[mid])l=mid+1;else r=mid-1;
80         }
81         ans+=(ll)(r-i);
82     }
83     cout<<ans<<endl;
84 
85     return 0;
86 
87 }