811. Subdomain Visit Count

https://leetcode.com/problems/subdomain-visit-count/

JavaScript

/**
 * @param {string[]} cpdomains
 * @return {string[]}
 */
var subdomainVisits = function(cpdomains) {
  const map = {}
  cpdomains.forEach(cpdomain => {
    const [count, domain] = cpdomain.split(' ')
    domain.split('.').reduceRight((ret, seg) => {
      ret.unshift(seg)
      const key = ret.join('.')
      map[key] = (map[key] || 0) + Number(count)
      return ret
    }, [])
  })
  return Object.keys(map).map(key => `${map[key]} ${key}`)
}

Python

class Solution:

    def subdomainVisits(self, cpdomains):
        """
        :type cpdomains: List[str]
        :rtype: List[str]
        """
        data = {}
        for cpdomain in cpdomains:
            count, domain = cpdomain.split(' ')
            domain = domain.split('.')[::-1]
            key = ''
            for seg in domain:
                key = seg if not key else (seg + '.' + key)
                data[key] = data.get(key, 0) + int(count)

        return ['%d %s' % (v, k) for k, v in data.items()]