1604. Alert Using Same Key-Card Three or More Times in a One Hour Period

Description

LeetCode company workers use key-cards to unlock office doors. Each time a worker uses their key-card, the security system saves the worker's name and the time when it was used. The system emits an alert if any worker uses the key-card three or more times in a one-hour period.

You are given a list of strings keyName and keyTime where [keyName[i], keyTime[i]] corresponds to a person's name and the time when their key-card was used in a single day.

Access times are given in the 24-hour time format "HH:MM", such as "23:51" and "09:49".

Return a list of unique worker names who received an alert for frequent keycard use. Sort the names in ascending order alphabetically.

Notice that "10:00" - "11:00" is considered to be within a one-hour period, while "22:51" - "23:52" is not considered to be within a one-hour period.

 

Example 1:

Input: keyName = ["daniel","daniel","daniel","luis","luis","luis","luis"], keyTime = ["10:00","10:40","11:00","09:00","11:00","13:00","15:00"]
Output: ["daniel"]
Explanation: "daniel" used the keycard 3 times in a one-hour period ("10:00","10:40", "11:00").

Example 2:

Input: keyName = ["alice","alice","alice","bob","bob","bob","bob"], keyTime = ["12:01","12:00","18:00","21:00","21:20","21:30","23:00"]
Output: ["bob"]
Explanation: "bob" used the keycard 3 times in a one-hour period ("21:00","21:20", "21:30").

 

Constraints:

  • 1 <= keyName.length, keyTime.length <= 105
  • keyName.length == keyTime.length
  • keyTime[i] is in the format "HH:MM".
  • [keyName[i], keyTime[i]] is unique.
  • 1 <= keyName[i].length <= 10
  • keyName[i] contains only lowercase English letters.

Solutions

Solution 1

Python Code
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class Solution:
    def alertNames(self, keyName: List[str], keyTime: List[str]) -> List[str]:
        d = defaultdict(list)
        for name, t in zip(keyName, keyTime):
            t = int(t[:2]) * 60 + int(t[3:])
            d[name].append(t)
        ans = []
        for name, ts in d.items():
            if (n := len(ts)) > 2:
                ts.sort()
                for i in range(n - 2):
                    if ts[i + 2] - ts[i] <= 60:
                        ans.append(name)
                        break
        ans.sort()
        return ans

Java Code
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class Solution {
    public List<String> alertNames(String[] keyName, String[] keyTime) {
        Map<String, List<Integer>> d = new HashMap<>();
        for (int i = 0; i < keyName.length; ++i) {
            String name = keyName[i];
            String time = keyTime[i];
            int t
                = Integer.parseInt(time.substring(0, 2)) * 60 + Integer.parseInt(time.substring(3));
            d.computeIfAbsent(name, k -> new ArrayList<>()).add(t);
        }
        List<String> ans = new ArrayList<>();
        for (var e : d.entrySet()) {
            var ts = e.getValue();
            int n = ts.size();
            if (n > 2) {
                Collections.sort(ts);
                for (int i = 0; i < n - 2; ++i) {
                    if (ts.get(i + 2) - ts.get(i) <= 60) {
                        ans.add(e.getKey());
                        break;
                    }
                }
            }
        }
        Collections.sort(ans);
        return ans;
    }
}

C++ Code
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class Solution {
public:
    vector<string> alertNames(vector<string>& keyName, vector<string>& keyTime) {
        unordered_map<string, vector<int>> d;
        for (int i = 0; i < keyName.size(); ++i) {
            auto name = keyName[i];
            auto time = keyTime[i];
            int a, b;
            sscanf(time.c_str(), "%d:%d", &a, &b);
            int t = a * 60 + b;
            d[name].emplace_back(t);
        }
        vector<string> ans;
        for (auto& [name, ts] : d) {
            int n = ts.size();
            if (n > 2) {
                sort(ts.begin(), ts.end());
                for (int i = 0; i < n - 2; ++i) {
                    if (ts[i + 2] - ts[i] <= 60) {
                        ans.emplace_back(name);
                        break;
                    }
                }
            }
        }
        sort(ans.begin(), ans.end());
        return ans;
    }
};

Go Code
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func alertNames(keyName []string, keyTime []string) (ans []string) {
	d := map[string][]int{}
	for i, name := range keyName {
		var a, b int
		fmt.Sscanf(keyTime[i], "%d:%d", &a, &b)
		t := a*60 + b
		d[name] = append(d[name], t)
	}
	for name, ts := range d {
		n := len(ts)
		if n > 2 {
			sort.Ints(ts)
			for i := 0; i < n-2; i++ {
				if ts[i+2]-ts[i] <= 60 {
					ans = append(ans, name)
					break
				}
			}
		}
	}
	sort.Strings(ans)
	return
}