leetcode451

public class Solution {
    public string FrequencySort(string s) {
        var dic = new Dictionary<char, int>();
            foreach (var c in s)
            {
                if (!dic.ContainsKey(c))
                {
                    dic.Add(c, );
                }
                else
                {
                    dic[c]++;
                }
            }

            var list = dic.OrderByDescending(x => x.Value).ToList();
            StringBuilder sb = new StringBuilder();
            foreach (var l in list)
            {
                var cha = l.Key;
                var times = l.Value;
                while (times > )
                {
                    sb.Append(cha);
                    times--;
                }
            }
            return sb.ToString();
    }
}

https://leetcode.com/problems/sort-characters-by-frequency/#/description

补充一个python的实现：

 import collections

 class Solution:
     def frequencySort(self, s: str) -> str:
         count = collections.Counter(s)
         li = sorted(count.items(), key=lambda d:d[], reverse = True)
         result = ''
         for i in range(len(li)):
             result += li[i][] * li[i][]
         return result