Top K Frequent Elements || Leetcode

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[physicsmadness]

why cant we use hashmap ....? I guess addition deletion are in constant time..I dont see any issue in using it..is there anything I am missing out.

[amanavengeraman]

MaxHeap will also have same time COmplexcity ??

[adityagarg]

Correct solution :-

class Solution {
public int[] topKFrequent(int[] nums, int k) {
PriorityQueue<int[]> pq =new PriorityQueue<>(k, (x, y) -> Integer.compare(y[1], x[1]));

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

for(int no : nums){
map.put(no, map.getOrDefault(no, 0) + 1);
}

for(int key : map.keySet()){
pq.offer(new int[] {key, map.get(key)});
}

int[] result = new int[k];

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

[atulsharma]

it is of time complexity of nlogk not n as min heap so addition long n, k elemnets therefore nlogk is time complexity

[aahanaganjewar]

class Solution {
public class Pair{
int key;
int value;
Pair (int key, int value) {
this.key = key;
this.value = value;
}


}

class Checker implements Comparator<Pair>
{
public int compare(Pair p1, Pair p2) {
if (p1.value < p2.value) {
return -1;
}
if (p1.value > p2.value) {
return 1;
}
return 0;
}
}
public int[] topKFrequent(int[] nums, int k) {
HashMap<Integer, Integer> hmap = new HashMap<>();
for (int num : nums) {
hmap.put(num, hmap.getOrDefault(num, 0) + 1);
}
PriorityQueue<Pair> pq = new PriorityQueue<>(5, new Checker());

for (int key : hmap.keySet()) {
if (pq.size() < k) {
pq.add(new Pair(key, hmap.get(key)));
} else {
if (hmap.get(key) > pq.peek().value) {
pq.remove();
pq.add(new Pair(key, hmap.get(key)));
}
}
}

int[] ans = new int[k];
for (int i = 0; i < k; i++) {
ans[i] = pq.remove().key;
}
return ans;
}
}

[AmanPandey-ordc]

I am a big admirer of pepcoding and really watch a lot but this explanation really isn't the level thata pepcoding gives. Very bad explanation. Please look into it.

[mickyman]

on the portal ques has random case where the 5 number has same freq and we k=3 any 3 random numbers, which gives wrong answer

[sulemankhan]

Please improve audio, there is lot of background voice

[vedanshbisht]

Bhai revision ker rha h ratke aya h 😂😂😂... kya bola kuch nahi samjha bro

[LegitGamer]

we can do better in average case using quick select