Revenge of Segment Tree

Problem Description

In computer science, a segment tree is a tree data structure for storing intervals, or segments. It allows querying which of the stored segments contain a given point. It is, in principle, a static structure; that is, its content cannot be modified once the structure is built. A similar data structure is the interval tree.
A segment tree for a set I of n intervals uses O(n log n) storage and can be built in O(n log n) time. Segment trees support searching for all the intervals that contain a query point in O(log n + k), k being the number of retrieved intervals or segments.
---Wikipedia

Today, Segment Tree takes revenge on you. As Segment Tree can answer the sum query of a interval sequence easily, your task is calculating the sum of the sum of all continuous sub-sequences of a given number sequence.

 

Input

The first line contains a single integer T, indicating the number of test cases. 

Each test case begins with an integer N, indicating the length of the sequence. Then N integer Ai follows, indicating the sequence.

[Technical Specification]
1. 1 <= T <= 10
2. 1 <= N <= 447 000
3. 0 <= Ai <= 1 000 000 000

 

Output

For each test case, output the answer mod 1 000 000 007.

 

Sample Input

 

Sample Output

 

Source

BestCoder Round #16

 

 

#include<cstdio>#include<iostream>#define mod 1000000007using namespace std;__int64 a[500000];__int64 sum;int main(){    __int64 i,j,n;    int t;    scanf("%d",&t);    while(t--)    {        scanf("%I64d",&n);        sum=0;        for(i=1;i<=n;i++)        {            scanf("%I64d",&a[i]);            sum+=a[i]*(i * (n - i + 1)%mod);// 主要注意这里会超long long 所以要在内部取余            sum%=mod;        }        printf("%I64d\n",sum);    }    return 0;}