Find the most frequent letters in a string.

Question

Liron · Accepted Answer

package com.google;

import java.io.ObjectInputStream.GetField;

public class FrequentLettre{
   
    public static char findFrequent(String str){
    	str = str.toLowerCase();
        char[] chars = str.toCharArray();
        int size = 'z'-'a'+1;
        int[] frequent = new int[size];
        for (char c : chars){
        	Character.getNumericValue('a');
        	Character.getNumericValue('p');
            ++frequent[c-'a'];
        }
        int max = frequent['a'-'a'];
        int maxInd = 0;
        for (int i=1; i max){
                max = frequent[i];
                maxInd = i;
            }
        }
        return (char) ('a'+maxInd);
    }
    
    public static void main (String[] args){
    	System.out.println(findFrequent("apple"));
    }
}

Giovanni · Answer

count sort

Sigiloso · Answer

Maybe store them as a hash table, keep track of the max. On every addition, if the recent added hash[letter] > hash[max], max = letter...return max

If we want to return multiple letters (say like in the word "letter" where e & t have the same frequency). We can store the  letters in an boolean array (which takes at most O(size of alphabet) space) and if hash[letter] = hash[max], set the array[letter] = true. Keep the same > & < rules as above but if one of them hits, set the array to false and set array[letter] = true. Return the boolean array or grab the true values and return those.

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