AcWing 3956. 截断数组（每日一题）

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 1e6+10;
int a[N],b[N],c[N],d[N];
//a接收数据 b前缀和 cd符合条件计数器
int main()
{
    long long cnt=0;
    int n;
    cin >> n;
    for (int i = 1; i <= n; i ++ )
    cin>>a[i];
    for (int i = 1; i <= n; i ++ )
    b[i]=a[i]+b[i-1];
    for (int i = 1; i < n; i ++ )
    {
        c[i]=c[i-1];
        if(b[i]*3==b[n])
        c[i]++;
    }
    for (int i = 2; i < n; i ++ )
    {
        d[i]=d[i-1];
        if(b[i]*3==b[n]*2)
        d[i]++;
    }
    for (int i = 1; i < n; i ++ )
    {
        if(b[i]*3==b[n])
            cnt+=(d[n-1]-d[i]);
    }
    cout << cnt;
}

AcWing 3956. 截断数组（每日一题） - AcWing