A:简单计算

#include <iostream>
using namespace std;
int main()
{
    int a, b, c, d;
    cin >> a >> b >> c >> d;

    int num = a * b + c * d;
    cout << num << endl;


    return 0;
}

B：餐厅
二分+前缀和：

#include <iostream>
#include <cstring>
using namespace std;
const int N = 2e5 + 10;
typedef long long LL;
LL s[N];
int n, q;
int binary (LL sum)
{
    int l = 0, r = n;
    while (l < r)
    {   
        int mid = l + r + 1>>1 ;
        if (s[mid] <= sum) l = mid;
        else r = mid - 1;
    }

    return n-l;
}
int main()
{

    cin >> n >> q;

    for (int i = 1; i <= n; i++)
    {
        int x;
        cin >> x;
        s[i] = s[i - 1] + x;
    }
    LL sum = 0;

    while (q--)
    {
        LL x;
        cin >> x;
        sum += x;

        if (sum >= s[n]) sum = 0;
        printf("%d\n", binary(sum));
    }

    return 0;
}