Formatted question description: https://leetcode.ca/all/1169.html

1169. Invalid Transactions (Medium)

A transaction is possibly invalid if:

  • the amount exceeds $1000, or;
  • if it occurs within (and including) 60 minutes of another transaction with the same name in a different city.

Each transaction string transactions[i] consists of comma separated values representing the name, time (in minutes), amount, and city of the transaction.

Given a list of transactions, return a list of transactions that are possibly invalid.  You may return the answer in any order.

 

Example 1:

Input: transactions = ["alice,20,800,mtv","alice,50,100,beijing"]
Output: ["alice,20,800,mtv","alice,50,100,beijing"]
Explanation: The first transaction is invalid because the second transaction occurs within a difference of 60 minutes, have the same name and is in a different city. Similarly the second one is invalid too.

Example 2:

Input: transactions = ["alice,20,800,mtv","alice,50,1200,mtv"]
Output: ["alice,50,1200,mtv"]

Example 3:

Input: transactions = ["alice,20,800,mtv","bob,50,1200,mtv"]
Output: ["bob,50,1200,mtv"]

 

Constraints:

  • transactions.length <= 1000
  • Each transactions[i] takes the form "{name},{time},{amount},{city}"
  • Each {name} and {city} consist of lowercase English letters, and have lengths between 1 and 10.
  • Each {time} consist of digits, and represent an integer between 0 and 1000.
  • Each {amount} consist of digits, and represent an integer between 0 and 2000.

Related Topics:
Array, String

Solution 1. Brute force

// OJ: https://leetcode.com/problems/invalid-transactions/

// Time: O(N^2)
// Space: O(N)
struct Transaction {
    string name;
    int time;
    int amount;
    string city;
    Transaction(string t) {
        istringstream ss(t);
        getline(ss, name, ',');
        string token;
        getline(ss, token, ',');
        time = stoi(token);
        getline(ss, token, ',');
        amount = stoi(token);
        ss >> city;
    }
};
class Solution {
public:
    vector<string> invalidTransactions(vector<string>& A) {
        vector<Transaction> B;
        unordered_set<int> invalid;
        for (int i = 0; i < A.size(); ++i) {
            auto t = Transaction(A[i]);
            if (t.amount > 1000) invalid.insert(i);
            B.push_back(t);
        }
        for (int i = 0; i < A.size(); ++i) {
            for (int j = i + 1; j < A.size(); ++j) {
                if (B[i].name == B[j].name && abs(B[i].time - B[j].time) <= 60 && B[i].city != B[j].city) {
                    invalid.insert(i);
                    invalid.insert(j);
                }
            }
        }
        vector<string> ans;
        for (int i : invalid) ans.push_back(A[i]);
        return ans;
    }
};

Solution 1. Sliding Window

// OJ: https://leetcode.com/problems/invalid-transactions/

// Time: O(NlogN)
// Space: O(N)
struct Transaction {
    string name;
    int time;
    int amount;
    string city;
    Transaction(string t) {
        istringstream ss(t);
        getline(ss, name, ',');
        string token;
        getline(ss, token, ',');
        time = stoi(token);
        getline(ss, token, ',');
        amount = stoi(token);
        ss >> city;
    }
};
class Solution {
public:
    vector<string> invalidTransactions(vector<string>& A) {
        unordered_map<string, vector<int>> m;
        vector<Transaction> B;
        unordered_set<int> invalid;
        for (int i = 0; i < A.size(); ++i) {
            auto t = Transaction(A[i]);
            if (t.amount > 1000) invalid.insert(i);
            m[t.name].push_back(i);
            B.push_back(t);
        }
        for (auto &[p, ids] : m) {
            sort(begin(ids), end(ids), [&](int a, int b) { return B[a].time < B[b].time; });
            int i = 0, j = 0, k = 0, N = ids.size();
            unordered_map<string, int> cities;
            while (j < N) {
                while (B[ids[j]].time - B[ids[i]].time > 60) {
                    auto &c = B[ids[i++]];
                    if (--cities[c.city] == 0) cities.erase(c.city);
                }
                if (B[ids[j]].time - B[ids[i]].time <= 60) {
                    auto &c = B[ids[j++]];
                    cities[c.city]++;
                    if (cities.size() > 1) {
                        for (k = max(k, i); k < j; ++k) invalid.insert(ids[k]);
                    }
                }
            }
        }
        vector<string> ans;
        for (int i : invalid) ans.push_back(A[i]);
        return ans;
    }
};

Java

class Solution {
    public List<String> invalidTransactions(String[] transactions) {
        int length = transactions.length;
        Transaction[] transactionsArray = new Transaction[length];
        for (int i = 0; i < length; i++) {
            String transactionStr = transactions[i];
            String[] array = transactionStr.split(",");
            String name = array[0];
            int time = Integer.parseInt(array[1]);
            int amount = Integer.parseInt(array[2]);
            String city = array[3];
            Transaction curTransaction = new Transaction(name, time, amount, city);
            transactionsArray[i] = curTransaction;
        }
        Arrays.sort(transactionsArray);
        Set<String> invalidSet = new HashSet<String>();
        Transaction transaction0 = transactionsArray[0];
        if (transaction0.amount > 1000)
            invalidSet.add(transaction0.toString());
        int prevIndex = 0;
        for (int i = 1; i < length; i++) {
            Transaction curTransaction = transactionsArray[i];
            if (curTransaction.amount > 1000)
                invalidSet.add(curTransaction.toString());
            while (!transactionsArray[prevIndex].name.equals(curTransaction.name) || curTransaction.time - transactionsArray[prevIndex].time > 60)
                prevIndex++;
            boolean flag = false;
            for (int j = prevIndex; j < i; j++) {
                Transaction prevTransaction = transactionsArray[j];
                if (curTransaction.name.equals(prevTransaction.name) && curTransaction.time - prevTransaction.time <= 60 && !curTransaction.city.equals(prevTransaction.city)) {
                    invalidSet.add(prevTransaction.toString());
                    flag = true;
                }
            }
            if (flag)
                invalidSet.add(curTransaction.toString());
        }
        List<String> invalidTransactionsList = new ArrayList<String>(invalidSet);
        return invalidTransactionsList;
    }
}

class Transaction implements Comparable<Transaction> {
    String name;
    int time;
    int amount;
    String city;

    public Transaction(String name, int time, int amount, String city) {
        this.name = name;
        this.time = time;
        this.amount = amount;
        this.city = city;
    }

    public int compareTo(Transaction transaction2) {
        if (!this.name.equals(transaction2.name))
            return this.name.compareTo(transaction2.name);
        else if (this.time != transaction2.time)
            return this.time - transaction2.time;
        else if (!this.city.equals(transaction2.city))
            return this.city.compareTo(transaction2.city);
        else
            return this.amount - transaction2.amount;
    }

    public String toString() {
        return name + "," + time + "," + amount + "," + city;
    }
}

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