Sort Characters By Frequency
Problem Statement - link #
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.
Examples #
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 * 10^5sconsists of uppercase and lowercase English letters and digits.
Solutions #
class Solution {
public:
string frequencySort(string s) {
map<char,int> mp;
int k=0;
multimap<int, char, greater<int>> mp2;
for(auto c: s) mp[c]++;
for(auto i: mp) mp2.insert({i.second,i.first});
for(auto i=mp2.begin(); i!=mp2.end(); i++)
for(auto j=0; j<i->first; j++){
s[k++] = i->second;
}
return s;
}
};