sorting/Comparator question at master · Anuj-3107/sorting · GitHub

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class Solution {
    public String frequencySort(String s) {

        // ArrayList<Character> a1=new ArrayList<>();
        // ArrayList<Integer> a2=new ArrayList<>();

        HashMap<Character,Integer> map=new HashMap<>();

        for(int i=0;i<s.length();i++)
        {
            // if(!a1.contains(s.charAt(i)))
            // {
            //     a1.add(s.charAt(i));
            //     a2.add(1);
            // }
            // else{
            //     a2.set(a1.indexOf(s.charAt(i)),a2.get(a1.indexOf(s.charAt(i)))+1);
            // }
            map.put(s.charAt(i),map.getOrDefault(s.charAt(i),0)+1);
        }


        // PriorityQueue<Character> pq = new PriorityQueue<>((a,b) -> a2.get(a1.indexOf(b)) - a2.get(a1.indexOf(a)));
        PriorityQueue<Character> pq = new PriorityQueue<>((a,b) -> map.get(b) - map.get(a));
        pq.addAll(map.keySet());

        String ans="";

        while(!pq.isEmpty())
        {
            char c=pq.poll();
            int m=map.get(c);
            while(m>0)
            {
                ans=ans+c;
                m--;
            }
        }

        return ans;
    }
}


# Priority Queue with comparator declaration

PriorityQueue<Integer> pq=new PriorityQueue<Integer>(new Comparator<Integer>()
                {
                    public int compare(Integer a, Integer b)
                    {
                        if(map.get(a)==map.get(b))
                        {
                            return a-b;
                        }
                        else{
                            return map.get(a)-map.get(b);
                        }
                    }
                });


# Sorting Array using comparator(Example)

class Solution {
    public int[][] kClosest(int[][] p, int k) {

        int ans[][]=new int[k][2];

        PriorityQueue<int[]> pq = new PriorityQueue<>((n1, n2) -> n1[0]*n1[0] + n1[1]*n1[1] - n2[0]*n2[0] - n2[1]*n2[1]);

        for (int[] temp : p)
        {
            pq.add(temp);
        }

        for (int i = 0; i < k; i++){
            ans[i] = pq.poll();
        }

        return ans;
    }
}


# IF-ELSE inside Arrays.sort

Arrays.sort(v, (a,b)->{
         if(a[0]==b[0])
         {
             return a[1]-b[1];
         }
        else{
             return a[0]-b[0];
        }
});