Given a string s, sort it in decreasing order based on the frequency of the characters. The frequency of a character is the number of times it appears in the string.
Return the sorted string. If there are multiple answers, return any of them.
Example 1:
Input: s = "tree" Output: "eert" Explanation: 'e' appears twice while 'r' and 't' both appear once. So 'e' must appear before both 'r' and 't'. Therefore "eetr" is also a valid answer.
Example 2:
Input: s = "cccaaa" Output: "aaaccc" Explanation: Both 'c' and 'a' appear three times, so both "cccaaa" and "aaaccc" are valid answers. Note that "cacaca" is incorrect, as the same characters must be together.
Example 3:
Input: s = "Aabb" Output: "bbAa" Explanation: "bbaA" is also a valid answer, but "Aabb" is incorrect. Note that 'A' and 'a' are treated as two different characters.
Constraints:
1 <= s.length <= 5 * 105s consists of uppercase and lowercase English letters and digits.class Solution {
public:
string frequencySort(string s) {
vector<string> v(10+26+26,"");
for(auto c:s)
if(c<='z' && c>='a')
v[c-'a'+10]+=c;
else if(c<='Z' && c>='A')
v[c-'A'+36]+=c;
else v[c-'0']+=c;
sort(v.begin(), v.end(), [](string a, string b){return a.size()>b.size();});
string res="";
for(auto x:v)
res+=x;
return res;
}
};