You're given two integers, A and B, representing the product numbers you want to observe.
The mall has placed a sensor in each customer's shopping cart, which can detect when a customer adds or removes items from the cart. The records stored by the sensor are a series of integers. A positive integer x indicates that the customer has added an item with the number x to their cart, while a negative integer -x indicates that the customer has removed an item with the number x from their cart.
Now there are records of N customers' shopping carts. You want to count how many customers ultimately purchased both products A and B. A customer is considered to have purchased a product X if the number of times the product X was added to their cart is greater than the number of times it was removed.
Sample Inputs/Outputs
| Sample Input(s) | Sample Output(s) |
|---|---|
| The first line contains two positive integers A and B (1 <= A, B <= 100). The second line contains a positive integer N (1 <= N <= 100), indicating the number of customers. Following that are N lines, where the i-th line represents the shopping cart records of the i-th customer. Each shopping cart record consists of a series of integers, with the last number always being 0, indicating the end of the shopping record. Other numbers are non-zero integers and their absolute values do not exceed 100, as defined in the problem statement. | Output an integer, indicating how many customers simultaneously purchased both products A and B. |
| 1 8 5 1 8 0 5 6 0 2 7 0 8 1 0 33 22 0 | 2 |
| 3 9 2 3 9 -3 3 9 0 3 3 -3 -3 9 0 | 1 |
Thought Process
When collecting shopping cart data, you can use EOF. You can use a Map to record the addition and removal of products. If a product is added, increment its count by 1; if it's removed, decrement its count by 1.
After collecting the data from each person, you can check if the counts of products A and B in the Map are greater than 0. If both products A and B are purchased by a customer, increment the answer by 1.
Sample Code－ZeroJudge F579: Shopping Cart
#include <iostream>
#include <map>
using namespace std;
int main() {
cin.sync_with_stdio(0);
cin.tie(0);
int a, b;
cin >> a >> b;
int N;
cin >> N;
int ans = 0;
for (int i = 0; i<N; i++)
{
int tmp;
map<int, int>MAP;
while (cin >> tmp && tmp != 0)
{
if (tmp > 0) MAP[tmp]++;
else MAP[tmp*-1]--;
}
if (MAP[a] > 0 && MAP[b] > 0) ans++;
}
cout << ans << "\n";
}
//ZeroJudge F579
//Dr. SeanXD