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84. Elements in an Array Occurring More Than N/K Times
Objective: Given an array of size of N and number k. Find all elements in an Array that appear more than N/K times.
Example:
int[] arrA = { 2, 2, 4, 4, 3, 5, 3, 4, 4, 6, 4, 3, 3, 8 };
K = 4
N/k = 14/4 = 3
Output:
4 appears more than n/ 4 times, Actual count is 5
3 appears more than n/ 4 times, Actual count is 4
Approach:
Naive Approach: Take nested for loops, check every element with all other elements, Time Complexity - O(n2) time.
Better Approach: Tetris Game technique- O(Nk)
- We will create a class structure that will store an element and its count.
class
Elements{
int element;
int count;
public Elements(
int element,
int count){
this.element = element;
this.count =count;
}
}
- Create array etms[] contains k-1 objects of class Elements with element =0 and count = 0.
- Navigate all the elements of the given array.
- Check if an element exists in etms[] if not, insert it with the count 1 and if exists then increase its count.
- Also check if etms[] gets full when inserting an element, if it is not, follow the previous step. If it is full then reduce the count of every existing element in the etms[]. (Just think of a Tetris game, when a row gets full, it gets deleted and the size of the Tetris is reduced by 1) see the picture below.
- Once all the elements of the array are over, check every element of etms[] with the array and print those elements that have N/K times.
Output:
4 appears more than n/4 times, Actual count is 5 3 appears more than n/4 times, Actual count is 4