Question

Write a method maxOccurrences that accepts a list of integers as a parameter and returns the number of times the most frequently occurring integer (the “mode”) occurs in the list. Solve this problem using a map as auxiliary storage. If the list is empty, return 0.

Answer 1

METHODS ARE WRITEN IN  TWO DIFFERENT WAYS:

METHOD 1 :

public int maxOccurrences(List<Integer> list)

{

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

int modeVal = 0;

for(int n : list)

{

if(map.containsKey(n))

{

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

}

else

{

map.put(n, 1);

}

if(map.get(n) > modVal)

modeVal = map.get(n);

}

return modeVal;

}

METHOD 2:

public static int maxOccurences(List<Integer> list)

{

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

Iterator<Integer> i = list.iterator();

while(i.hasNext())

{

int num = i.next();

if(map.containsKey(num))

{

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

}

else

{

map.put(num,1);

}

}

set<Integer> setKey = map.keySet();

i = setKey.iterator();

int max = 0;

while(i.hasNext())

{

int current = map.get(i.next());

if(current > max)

{

max = current;

}

}

return max;

}