811. Subdomain Visit Count #

Problem #

A website domain like “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.

Now, call a “count-paired domain” to be a count (representing the number of visits this domain received), followed by a space, followed by the address. An example of a count-paired domain might be “9001 discuss.leetcode.com”.

We are given a list cpdomains of count-paired domains. We would like a list of count-paired domains, (in the same format as the input, and in any order), that explicitly counts the number of visits to each subdomain.

Example 1:

Input: 
["9001 discuss.leetcode.com"]
Output: 
["9001 discuss.leetcode.com", "9001 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: 
["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.

Notes:

• The length of cpdomains will not exceed 100.
• The length of each domain name will not exceed 100.
• Each address will have either 1 or 2 “.” characters.
• The input count in any count-paired domain will not exceed 10000.
• The answer output can be returned in any order.

Problem Summary #

A website domain, such as “discuss.leetcode.com”, contains multiple subdomains. As a top-level domain, a common one is “com”; the next level is “leetcode.com”; and the lowest level is “discuss.leetcode.com”. When we visit the domain “discuss.leetcode.com”, we also simultaneously visit its parent domain “leetcode.com” and the top-level domain “com”. Given a combination of visit count and domain name, compute the number of visits for each domain separately. Its format is visit count + space + address, for example: “9001 discuss.leetcode.com”.

Next, a list cpdomains of visit-count and domain-name combinations will be given. Parse the visit counts of all domains and output them in the same format as the input format, with no restriction on order.

Solution Ideas #

• This is an easy problem: count the occurrence frequency of each domain. For each domain, according to its levels, accumulate the frequency level by level. For example, for discuss.leetcode.com, the frequency of the domain discuss.leetcode.com is 1, the frequency of the domain leetcode.com is 1, and the frequency of the domain com is 1. Use a map to count the occurrence frequency of each domain in order, and output according to the required format.

Code #

package leetcode

import (
	"strconv"
	"strings"
)

// Solution 1
func subdomainVisits(cpdomains []string) []string {
	result := make([]string, 0)
	if len(cpdomains) == 0 {
		return result
	}
	domainCountMap := make(map[string]int, 0)
	for _, domain := range cpdomains {
		countDomain := strings.Split(domain, " ")
		allDomains := strings.Split(countDomain[1], ".")
		temp := make([]string, 0)
		for i := len(allDomains) - 1; i >= 0; i-- {
			temp = append([]string{allDomains[i]}, temp...)
			ld := strings.Join(temp, ".")
			count, _ := strconv.Atoi(countDomain[0])
			if val, ok := domainCountMap[ld]; !ok {
				domainCountMap[ld] = count
			} else {
				domainCountMap[ld] = count + val
			}
		}
	}
	for k, v := range domainCountMap {
		t := strings.Join([]string{strconv.Itoa(v), k}, " ")
		result = append(result, t)
	}
	return result
}

// Solution 2
func subdomainVisits1(cpdomains []string) []string {
	out := make([]string, 0)
	var b strings.Builder
	domains := make(map[string]int, 0)
	for _, v := range cpdomains {
		splitDomain(v, domains)
	}
	for k, v := range domains {
		b.WriteString(strconv.Itoa(v))
		b.WriteString(" ")
		b.WriteString(k)
		out = append(out, b.String())
		b.Reset()
	}
	return out
}

func splitDomain(domain string, domains map[string]int) {
	visits := 0
	var e error
	subdomains := make([]string, 0)
	for i, v := range domain {
		if v == ' ' {
			visits, e = strconv.Atoi(domain[0:i])
			if e != nil {
				panic(e)
			}
			break
		}
	}
	for i := len(domain) - 1; i >= 0; i-- {
		if domain[i] == '.' {
			subdomains = append(subdomains, domain[i+1:])
		} else if domain[i] == ' ' {
			subdomains = append(subdomains, domain[i+1:])
			break
		}
	}
	for _, v := range subdomains {
		count, ok := domains[v]
		if ok {
			domains[v] = count + visits
		} else {
			domains[v] = visits
		}
	}
}