Problem
Given a string, sort it in decreasing order based on the frequency of characters.
Example 1:
Input: "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: "cccaaa" Output: "cccaaa"
Explanation:
Both "c" and "a" appear three times, so "aaaccc" is also a valid answer.
Note that "cacaca" is incorrect, as the same characters must be together.
Example 3:
Input: "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.
class Solution { public String frequencySort(String s) { MapBucket Sortmap = new HashMap<>(); for (int i = 0; i < s.length(); i++) { map.put(s.charAt(i), map.getOrDefault(s.charAt(i), 0)+1); } PriorityQueue > queue = new PriorityQueue<>((a, b)->b.getValue()-a.getValue()); queue.addAll(map.entrySet()); StringBuilder sb = new StringBuilder(); while (!queue.isEmpty()) { Map.Entry entry = queue.poll(); for (int i = 0; i < (int)entry.getValue(); i++) sb.append(entry.getKey()); } return sb.toString(); } }
class Solution { public String frequencySort(String s) { Mapmap = new HashMap<>(); for (int i = 0; i < s.length(); i++) { map.put(s.charAt(i), map.getOrDefault(s.charAt(i), 0)+1); } List [] buckets = new ArrayList[s.length()+1]; for (Map.Entry entry: map.entrySet()) { int i = entry.getValue(); if (buckets[i] == null) buckets[i] = new ArrayList<>(); buckets[i].add(entry.getKey()); } StringBuilder sb = new StringBuilder(); for (int i = s.length(); i >= 0; i--) { if (buckets[i] != null && buckets[i].size() > 0) { for (Character ch: buckets[i]) { for (int j = i; j > 0; j--) sb.append(ch); } } } return sb.toString(); } }
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