C. Eugene and an array（Round #632 Div 2）前缀和

Eugene likes working with arrays. And today he needs your help in solving one challenging task.

An array c is a subarray of an array b if c can be obtained from b by deletion of several (possibly, zero or all) elements from the beginning and several (possibly, zero or all) elements from the end.

Let’s call a nonempty array good if for every nonempty subarray of this array, sum of the elements of this subarray is nonzero. For example, array [−1,2,−3] is good, as all arrays [−1], [−1,2], [−1,2,−3], [2], [2,−3], [−3] have nonzero sums of elements. However, array [−1,2,−1,−3] isn’t good, as his subarray [−1,2,−1] has sum of elements equal to 0.

Help Eugene to calculate the number of nonempty good subarrays of a given array a.

Input
The first line of the input contains a single integer n (1≤n≤2×105) — the length of array a.

The second line of the input contains n integers a1,a2,…,an (−109≤ai≤109) — the elements of a.

Output
Output a single integer — the number of good subarrays of a.

Examples
inputCopy
3
1 2 -3
outputCopy
5
inputCopy
3
41 -41 41
outputCopy
3
Note
In the first sample, the following subarrays are good: [1], [1,2], [2], [2,−3], [−3]. However, the subarray [1,2,−3] isn’t good, as its subarray [1,2,−3] has sum of elements equal to 0.

In the second sample, three subarrays of size 1 are the only good subarrays. At the same time, the subarray [41,−41,41] isn’t good, as its subarray [41,−41] has sum of elements equal to 0.

点击进入题目

题意：就是给你一个字符串，叫你去找其中和不为零的子串数目。

思路：用前缀和

#include
using namespace std;
typedef long long ll;
map<ll,int>pos;

int main()
{
    int n;
    cin>>n;
    int q = -1;
    ll ans = 0,sum=0;
    pos[0]=0;
    for(int i=1;i<=n;i++)
    {
        int x; cin>>x;
        sum+=x;
        if(pos.count(sum)) q = max(q,pos[sum]);//更新最左边的位置
        ans +=i-q-1;
        pos[sum] = i;
    }
    cout<<ans<<endl;
    return 0;
}