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811. Subdomain Visit Count

Description

A website domain "discuss.leetcode.com" consists of various subdomains. At the top level, we have "com", at the next level, we have "leetcode.com" and at the lowest level, "discuss.leetcode.com". When we visit a domain like "discuss.leetcode.com", we will also visit the parent domains "leetcode.com" and "com" implicitly.

A count-paired domain is a domain that has one of the two formats "rep d1.d2.d3" or "rep d1.d2" where rep is the number of visits to the domain and d1.d2.d3 is the domain itself.

  • For example, "9001 discuss.leetcode.com" is a count-paired domain that indicates that discuss.leetcode.com was visited 9001 times.

Given an array of count-paired domains cpdomains, return an array of the count-paired domains of each subdomain in the input. You may return the answer in any order.

 

Example 1:

Input: cpdomains = ["9001 discuss.leetcode.com"]
Output: ["9001 leetcode.com","9001 discuss.leetcode.com","9001 com"]
Explanation: We only have one website domain: "discuss.leetcode.com".
As discussed above, the subdomain "leetcode.com" and "com" will also be visited. So they will all be visited 9001 times.

Example 2:

Input: cpdomains = ["900 google.mail.com", "50 yahoo.com", "1 intel.mail.com", "5 wiki.org"]
Output: ["901 mail.com","50 yahoo.com","900 google.mail.com","5 wiki.org","5 org","1 intel.mail.com","951 com"]
Explanation: We will visit "google.mail.com" 900 times, "yahoo.com" 50 times, "intel.mail.com" once and "wiki.org" 5 times.
For the subdomains, we will visit "mail.com" 900 + 1 = 901 times, "com" 900 + 50 + 1 = 951 times, and "org" 5 times.

 

Constraints:

  • 1 <= cpdomain.length <= 100
  • 1 <= cpdomain[i].length <= 100
  • cpdomain[i] follows either the "repi d1i.d2i.d3i" format or the "repi d1i.d2i" format.
  • repi is an integer in the range [1, 104].
  • d1i, d2i, and d3i consist of lowercase English letters.

Solutions

Use a map to store each subdomain and the number of times the subdomain is visited. For each count-paired domains in cpdomains, split the count and the domain, and add the count to each subdomain’s count. Finally, loop over the map to get each subdomain’s number of visits.

  • class Solution {
    public List<String> subdomainVisits(String[] cpdomains) {
        Map<String, Integer> cnt = new HashMap<>();
        for (String s : cpdomains) {
            int i = s.indexOf(" ");
            int v = Integer.parseInt(s.substring(0, i));
            for (; i < s.length(); ++i) {
                if (s.charAt(i) == ' ' || s.charAt(i) == '.') {
                    String t = s.substring(i + 1);
                    cnt.put(t, cnt.getOrDefault(t, 0) + v);
                }
            }
        }
        List<String> ans = new ArrayList<>();
        for (var e : cnt.entrySet()) {
            ans.add(e.getValue() + " " + e.getKey());
        }
        return ans;
    }
}

  • class Solution {
public:
    vector<string> subdomainVisits(vector<string>& cpdomains) {
        unordered_map<string, int> cnt;
        for (auto& s : cpdomains) {
            int i = s.find(' ');
            int v = stoi(s.substr(0, i));
            for (; i < s.size(); ++i) {
                if (s[i] == ' ' || s[i] == '.') {
                    cnt[s.substr(i + 1)] += v;
                }
            }
        }
        vector<string> ans;
        for (auto& [s, v] : cnt) {
            ans.push_back(to_string(v) + " " + s);
        }
        return ans;
    }
};

  • from collections import Counter

class Solution:
    def subdomainVisits(self, cpdomains: List[str]) -> List[str]:
        cnt = Counter()
        for s in cpdomains:
            v = int(s[: s.index(' ')])
            for i, c in enumerate(s):
                if c in ' .': # space ' ' is for the full domain, and '.' for subdomain
                    cnt[s[i + 1 :]] += v
        return [f'{v} {s}' for s, v in cnt.items()]

############

class Solution(object):
    def subdomainVisits(self, cpdomains):
        """
        :type cpdomains: List[str]
        :rtype: List[str]
        """
        domain_counts = collections.defaultdict(int)
        for cpdomain in cpdomains:
            times, domains = cpdomain.split()
            times = int(times)
            domain_counts[domains] += times
            while '.' in domains:
                domains = domains[domains.index('.') + 1:]
                domain_counts[domains] += times
        return [str(v) + ' ' + d for d, v in domain_counts.items()]


  • func subdomainVisits(cpdomains []string) []string {
	cnt := map[string]int{}
	for _, s := range cpdomains {
		i := strings.IndexByte(s, ' ')
		v, _ := strconv.Atoi(s[:i])
		for ; i < len(s); i++ {
			if s[i] == ' ' || s[i] == '.' {
				cnt[s[i+1:]] += v
			}
		}
	}
	ans := make([]string, 0, len(cnt))
	for s, v := range cnt {
		ans = append(ans, strconv.Itoa(v)+" "+s)
	}
	return ans
}

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