LeetCode 2228: Users With Two Purchases Within Seven Days
Problem Description
Explanation:
To solve this problem, we can iterate over the transactions and keep track of the user IDs along with their purchase timestamps. For each user, we maintain a list of timestamps in ascending order. Then, we iterate over each user's purchase timestamps to find if there are at least two purchases within seven days. :
Solutions
class Solution {
public int numUsersWithTwoPurchasesWithinSevenDays(int[][] purchases) {
Map<Integer, List<Integer>> userPurchases = new HashMap<>();
int count = 0;
for (int[] purchase : purchases) {
int userId = purchase[0];
int timestamp = purchase[1];
userPurchases.putIfAbsent(userId, new ArrayList<>());
userPurchases.get(userId).add(timestamp);
}
for (List<Integer> timestamps : userPurchases.values()) {
if (timestamps.size() < 2) continue;
Collections.sort(timestamps);
for (int i = 0; i < timestamps.size() - 1; i++) {
int j = i + 1;
while (j < timestamps.size() && timestamps.get(j) - timestamps.get(i) <= 7) {
if (j - i >= 1) {
count++;
break;
}
j++;
}
}
}
return count;
}
}Loading editor...