package leetcode;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

public class TopKFrequent {

public List<Integer> topKFrequent(int[] nums, int k) {

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

for (int num : nums) {

if(map.containsKey(num)){

map.put(num, map.get(num) + 1);

}

else

map.put(num, 1);

}

int[][] arr = new int[map.size()][2];

int index = 0;

for(int num:map.keySet()){

int[] temp = {map.get(num),num};

arr[index++] = temp;

}

ArrayList<Integer> ret = new ArrayList<Integer>();

topK(arr, k, 0, arr.length-1);

int pointer = arr.length-1;

while(ret.size() < k && pointer >=0)

ret.add(arr[pointer--][1]);

return ret;

}

private void topK(int[][] arr,int k,int start, int end){

if(start >= end)

return;

int pivotIndex = start;

int initialEnd = end;

int pivot = arr[pivotIndex][0];

while(start < end){

while(start<= end && arr[start][0] <= pivot)

start++;

while(start<= end && arr[end][0] >= pivot)

end--;

if(start < end && arr[start][0] > pivot && arr[end][0] < pivot)

swap(arr, start++, end--);

}

swap(arr, pivotIndex, end);

int top = arr.length - (end + 1);

if(top == k)

return;

else if (top > k) {

topK(arr, k, end + 1, initialEnd);

}

else{

topK(arr, k, pivotIndex, end - 1);

}

}

private void swap(int[][] arr,int i,int j){

int[] temp = arr[i];

arr[i] = arr[j];

arr[j] = temp;

}

public static void main(String[] args) {

int[] nums = {1,1,2,2,3,4,5,6,7};

TopKFrequent tf = new TopKFrequent();

for(int num:tf.topKFrequent(nums, 2)){

System.out.println(num);

}

}

}