811. Subdomain Visit Count

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.

题意：给出域名模式的字符串，要求求出每个域名(每级域名)的出现次数。主要涉及map映射与字符串的分割。

class Solution {
public:
    vector<string> subdomainVisits(vector<string>& cp) {
        // 使用了unrodered_map 实现哈希映射
        unordered_map<string,int>mp;
        vector<string>vec;
        string str;
        for(int i=0;i<cp.size();i++){
            int k=0,num=0;
            // 计算数字
            while(cp[i][k]!=' '){
                num=num*10+cp[i][k]-'0';
                k++;
            }
            // string.substr(pos,len) 获得string的字串，从pos位置开始，长度为len
            mp[cp[i].substr(k+1,cp[i].length()-k)]+=num;
            while(k<cp[i].length()){
                if(cp[i][k]=='.'){
                    mp[cp[i].substr(k+1,cp[i].length()-k)]+=num;
                }
                k++;
            }
        } 
        // 遍历mp    to_string c++11中新出的函数，可以将一个int整型转化为string类型
        for(auto it:mp){
            str=to_string(it.second);
            str+=" ";
            str+=it.first;
            vec.push_back(str);
        }
        return vec;
    }
};