811. Subdomain Visit Count

Medium

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, 10^4].

• d1i, d2i, and d3i consist of lowercase English letters.

解題

func subdomainVisits(cpdomains []string) []string {
    m := make(map[string]int) // 記錄每個網域被拜訪的次數

    for _, s := range cpdomains {
        arr := strings.Fields(s) // 將次數與domain name 分開
        times, domain := arr[0], arr[1]
        time, err := strconv.Atoi(times) // 將次數轉為次數，才能做加法
        if err != nil { fmt.Println(err) }

        m[domain] += time // 將一開始的domain次數記錄起來
        for i:=0; i<len(domain); i++ {
            if domain[i] == '.' { // 依序遞迴subdomain
                m[domain[i+1:]] += time // 記錄subdomain被拜訪的次數
            }
        }
    }
    
    ans := make([]string, 0)
    for key := range m {
        ans = append(ans, strconv.Itoa(m[key]) + " " + key)
    }

    return ans
}