HDU 5288 OO’s Sequence
OO’s Sequence
Time Limit: 4000/2000 MS (Java/Others) Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 2927 Accepted Submission(s): 1041
Problem Description
OO has got a array A of size n ,defined a function f(l,r) represent the number of i (l<=i<=r) , that there's no j(l<=j<=r,j<>i) satisfy ai mod aj=0,now OO want to know
∑i=1n∑j=inf(i,j) mod (109+7).
Input
There are multiple test cases. Please process till EOF.
In each test case:
First line: an integer n(n<=10^5) indicating the size of array
Second line:contain n numbers ai(0<ai<=10000)
In each test case:
First line: an integer n(n<=10^5) indicating the size of array
Second line:contain n numbers ai(0<ai<=10000)
Output
For each tests: ouput a line contain a number ans.
Sample Input
5
1 2 3 4 5
Sample Output
23
/* ∑i=1-n ∑j=i-n f(i,j) 其实是在求对于任一个i满足与其他成员互质的区间个数 则就可以采用类似线性筛的方法,将i的左右端点给记录下来 */ #include<iostream> #include<cstdio> #include<cstring> #include<cmath> using namespace std; typedef long long LL; const int mod=1000000007; #define N 100005 int a[N]; int Hasha[10005],Hashb[10005]; int positiona[N],positionb[N]; int main(){ int x; int sum; int i,j,k; while(~scanf("%d",&x)){ sum=0; memset(Hasha,0,sizeof(Hasha)); for(i=1;i<=10000;i++) Hashb[i]=x+1; for(i=1;i<=x;i++) scanf("%d",&a[i]); for(i=1;i<=x;i++){ positiona[i]=Hasha[a[i]]; for(j=a[i];j<10005;j+=a[i]) Hasha[j]=i; } for(i=x;i>=1;i--){ positionb[i]=Hashb[a[i]]-1; for(j=a[i];j<10005;j+=a[i]) Hashb[j]=i; } for(i=1;i<=x;i++){ //printf("%lld %lld\n",positiona[i],positionb[i]); sum=(sum+(i-positiona[i])*(positionb[i]+1-i))%mod; } printf("%d\n",sum); } return 0; }