Sort Characters By Frequency solution and explanation

def frequencySort(s: str) -> str:
    from collections import Counter
    freq_map = Counter(s)
    sorted_chars = sorted(freq_map.items(), key=lambda x: -x[1])
    return ''.join(char * freq for char, freq in sorted_chars)

import java.util.*;

class Solution {
    public String frequencySort(String s) {
        Map<Character, Integer> freqMap = new HashMap<>();
        for (char c : s.toCharArray()) {
            freqMap.put(c, freqMap.getOrDefault(c, 0) + 1);
        }
        List<Map.Entry<Character, Integer>> list = new ArrayList<>(freqMap.entrySet());
        list.sort((a, b) -> b.getValue() - a.getValue());
        StringBuilder result = new StringBuilder();
        for (Map.Entry<Character, Integer> entry : list) {
            result.append(String.valueOf(entry.getKey()).repeat(entry.getValue()));
        }
        return result.toString();
    }
}

#include <string>
#include <unordered_map>
#include <vector>
#include <algorithm>

std::string frequencySort(std::string s) {
    std::unordered_map<char, int> freq_map;
    for (char c : s) {
        ++freq_map[c];
    }
    std::vector<std::pair<int, char>> freq_vector;
    for (const auto& pair : freq_map) {
        freq_vector.emplace_back(pair.second, pair.first);
    }
    std::sort(freq_vector.begin(), freq_vector.end(), std::greater<>());
    std::string result;
    for (const auto& pair : freq_vector) {
        result += std::string(pair.first, pair.second);
    }
    return result;
}

function frequencySort(s) {
    const freqMap = {};
    for (const char of s) {
        freqMap[char] = (freqMap[char] || 0) + 1;
    }
    const sortedChars = Object.entries(freqMap).sort((a, b) => b[1] - a[1]);
    return sortedChars.map(([char, freq]) => char.repeat(freq)).join('');
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int cmpFunc(const void *a, const void *b) {
    return (*(int*)b - *(int*)a);
}

char* frequencySort(char* s) {
    int freq[256] = {0};
    int len = strlen(s);
    for (int i = 0; i < len; i++) {
        freq[(int)s[i]]++;
    }

    int charList[256];
    for (int i = 0; i < 256; i++) charList[i] = i;

    qsort(charList, 256, sizeof(int), cmpFunc);

    char* result = (char*)malloc(len + 1);
    int index = 0;
    for (int i = 0; i < 256 && index < len; i++) {
        char c = (char)charList[i];
        while (freq[c]-- > 0) {
            result[index++] = c;
        }
    }
    result[len] = '\0';
    return result;
}

using System;
using System.Collections.Generic;
using System.Linq;

public class Solution {
    public string FrequencySort(string s) {
        var freqMap = new Dictionary<char, int>();
        foreach (char c in s) {
            if (!freqMap.ContainsKey(c)) freqMap[c] = 0;
            freqMap[c]++;
        }
        var sortedChars = freqMap.OrderByDescending(pair => pair.Value);
        return string.Concat(sortedChars.Select(pair => new string(pair.Key, pair.Value)));
    }
}

def frequencySort(s: str) -> str:
    from collections import defaultdict
    freq_map = defaultdict(int)
    for char in s:
        freq_map[char] += 1
    max_freq = max(freq_map.values())
    buckets = [[] for _ in range(max_freq + 1)]
    for char, freq in freq_map.items():
        buckets[freq].append(char)
    result = []
    for freq in range(max_freq, 0, -1):
        for char in buckets[freq]:
            result.append(char * freq)
    return ''.join(result)

import java.util.*;

class Solution {
    public String frequencySort(String s) {
        Map<Character, Integer> freqMap = new HashMap<>();
        int maxFreq = 0;
        for (char c : s.toCharArray()) {
            int freq = freqMap.getOrDefault(c, 0) + 1;
            freqMap.put(c, freq);
            if (freq > maxFreq) maxFreq = freq;
        }
        List<Character>[] buckets = new List[maxFreq + 1];
        for (int i = 0; i <= maxFreq; i++) {
            buckets[i] = new ArrayList<>();
        }
        for (char key : freqMap.keySet()) {
            int freq = freqMap.get(key);
            buckets[freq].add(key);
        }
        StringBuilder sb = new StringBuilder();
        for (int i = maxFreq; i > 0; i--) {
            for (char c : buckets[i]) {
                sb.append(String.valueOf(c).repeat(i));
            }
        }
        return sb.toString();
    }
}

#include <string>
#include <vector>
#include <unordered_map>

std::string frequencySort(std::string s) {
    std::unordered_map<char, int> freq_map;
    int max_freq = 0;
    for (char c : s) {
        max_freq = std::max(max_freq, ++freq_map[c]);
    }
    std::vector<std::vector<char>> buckets(max_freq + 1);
    for (const auto& pair : freq_map) {
        buckets[pair.second].push_back(pair.first);
    }
    std::string result;
    for (int freq = max_freq; freq > 0; --freq) {
        for (char c : buckets[freq]) {
            result.append(freq, c);
        }
    }
    return result;
}

function frequencySort(s) {
    const freqMap = {};
    let maxFreq = 0;
    for (const char of s) {
        freqMap[char] = (freqMap[char] || 0) + 1;
        maxFreq = Math.max(maxFreq, freqMap[char]);
    }
    const buckets = Array.from({ length: maxFreq + 1 }, () => []);
    for (const char in freqMap) {
        const freq = freqMap[char];
        buckets[freq].push(char);
    }
    let result = '';
    for (let i = maxFreq; i > 0; i--) {
        for (const char of buckets[i]) {
            result += char.repeat(i);
        }
    }
    return result;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char* frequencySort(char* s) {
    int freq[256] = {0};
    int len = strlen(s);
    for (int i = 0; i < len; i++) {
        freq[(int)s[i]]++;
    }
    char* result = (char*)malloc(len + 1);
    int index = 0;
    for (int i = len; i > 0; i--) {
        for (int j = 0; j < 256; j++) {
            if (freq[j] == i) {
                for (int k = 0; k < i; k++) {
                    result[index++] = (char)j;
                }
            }
        }
    }
    result[len] = '\0';
    return result;
}

using System;
using System.Collections.Generic;
using System.Linq;

public class Solution {
    public string FrequencySort(string s) {
        var freqMap = new Dictionary<char, int>();
        int maxFreq = 0;
        foreach (var c in s) {
            if (!freqMap.ContainsKey(c)) freqMap[c] = 0;
            maxFreq = Math.Max(maxFreq, ++freqMap[c]);
        }
        var buckets = new List<char>[maxFreq + 1];
        for (int i = 0; i <= maxFreq; i++) buckets[i] = new List<char>();
        foreach (var kvp in freqMap) {
            buckets[kvp.Value].Add(kvp.Key);
        }
        var result = new System.Text.StringBuilder();
        for (int i = maxFreq; i > 0; i--) {
            foreach (var c in buckets[i]) {
                result.Append(c, i);
            }
        }
        return result.ToString();
    }
}

function frequencySort(s: string): string {
    const cnt: Map<string, number> = new Map();
    for (const c of s) {
        cnt.set(c, (cnt.get(c) || 0) + 1);
    }
    const cs = Array.from(cnt.keys()).sort((a, b) => cnt.get(b)! - cnt.get(a)!);
    const ans: string[] = [];
    for (const c of cs) {
        ans.push(c.repeat(cnt.get(c)!));
    }
    return ans.join('');
}

func frequencySort(s string) string {
	cnt := map[byte]int{}
	for i := range s {
		cnt[s[i]]++
	}
	cs := make([]byte, 0, len(s))
	for c := range cnt {
		cs = append(cs, c)
	}
	sort.Slice(cs, func(i, j int) bool { return cnt[cs[i]] > cnt[cs[j]] })
	ans := make([]byte, 0, len(s))
	for _, c := range cs {
		ans = append(ans, bytes.Repeat([]byte{c}, cnt[c])...)
	}
	return string(ans)
}

use std::collections::HashMap;
impl Solution {
    pub fn frequency_sort(s: String) -> String {
        let mut cnt = HashMap::new();
        for c in s.chars() {
            cnt.insert(c, cnt.get(&c).unwrap_or(&0) + 1);
        }
        let mut cs = cnt.into_iter().collect::<Vec<(char, i32)>>();
        cs.sort_unstable_by(|(_, a), (_, b)| b.cmp(&a));
        cs.into_iter()
            .map(|(c, v)| vec![c; v as usize].into_iter().collect::<String>())
            .collect()
    }
}

class Solution {
    /**
     * @param String $s
     * @return String
     */
    function frequencySort($s) {
        $cnt = array_count_values(str_split($s));
        $cs = array_keys($cnt);
        usort($cs, function ($a, $b) use ($cnt) {
            return $cnt[$b] <=> $cnt[$a];
        });
        $ans = '';
        foreach ($cs as $c) {
            $ans .= str_repeat($c, $cnt[$c]);
        }
        return $ans;
    }
}