asked on

wordcount challenge

Hi,

I am working on below challenge.
http://codingbat.com/prob/p117630

The classic word-count algorithm: given an array of strings, return a Map<String, Integer> with a key for each different string, with the value the number of times that string appears in the array.

wordCount(["a", "b", "a", "c", "b"]) → {"b": 2, "c": 1, "a": 2}
wordCount(["c", "b", "a"]) → {"b": 1, "c": 1, "a": 1}
wordCount(["c", "c", "c", "c"]) → {"c": 4}

do i need to worry about sorting like alphabetica in output?

ASKER CERTIFIED SOLUTION

Am P

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SOLUTION

zzynx

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gudii9

ASKER

public Map<String, Integer> wordCount(String[] strings) {
  Map<String, Integer> map=new HashMap();
  for(int i=0;i<strings.length;i++){
  String test=strings[i];
  if(map.containsKey(test)){
  int count=map.get(test);
  map.put(test,count+1);
  }
  
  else{
  map.put(test,1);
  }
}
  return map;
}

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above passes all tests. any improvements or alternate approaches.

gudii9

ASKER

public Map < String, Integer > wordCount(String[] strings) {
    Map < String, Integer > map = new SortedMap();
    for (int i = 0; i < strings.length; i++) {
        String test = strings[i];
        if (map.containsKey(test)) {
            int count = map.get(test);
            map.put(test, count + 1);
        } else {
            map.put(test, 1);
        }
    }
    return map;
}

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why above gives below compilation error?

Compile problems:

Error: Map<String, Integer> map=new SortedMap();
^^^^^^^^^
Cannot instantiate the type SortedMap

see Example Code to help with compile problems

does not codingbat supports SortedMap?

phoffric

Working with SortedMap in this question is off-topic as the challenge questions requires you to use a Map.
You should look up the SortedMap API if you want to ask another question.

gudii9

ASKER

SortedMap is implementation of Map interface similar to HashMap right? I thought codingbat supports that as well but looks no. Only HashMap? I will test in ecipse and see how it works

gudii9

ASKER

looks like no SortedMap class is there. It seems to be interface. TreeMap is only implenetation class.
https://www.tutorialspoint.com/java/java_sortedmap_interface.htm

gudii9

ASKER

package test;

import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;

public class WordCount {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		// wordCount(["a", "b", "a", "c", "b"]) → {"b": 2, "c": 1, "a": 2}
		// Map<String, String> map = new HashMap();
		// map.put("b", null);
		// map.put("a", "Hi");
		String[] arr = { "a", "b", "a", "c", "b" };
		System.out.println("--->" + mapAB(arr));

	}

	/*
	 * private static String mapAB(String[] arr) { // TODO Auto-generated method
	 * stub return null; }
	 */

	public Map<String, Integer> wordCount(String[] strings) {
		Map<String, Integer> map = new TreeMap();
		for (int i = 0; i < strings.length; i++) {
			String test = strings[i];
			if (map.containsKey(test)) {
				int count = map.get(test);
				map.put(test, count + 1);
			}

			else {
				map.put(test, 1);
			}
		}
		return map;
	}

}

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above gives below error at line at line 9

The method mapAB(String[]) is undefined for the type WordCount

Not sure why and how to fix it?

gudii9

ASKER

package test;

import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;

public class WordCount {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		// wordCount(["a", "b", "a", "c", "b"]) → {"b": 2, "c": 1, "a": 2}
		// Map<String, String> map = new HashMap();
		// map.put("b", null);
		// map.put("a", "Hi");
		String[] arr = { "a", "b", "a", "c", "b" };
		System.out.println("--->" + wordCount(arr));

	}

	/*
	 * private static String mapAB(String[] arr) { // TODO Auto-generated method
	 * stub return null; }
	 */

	public static Map<String, Integer> wordCount(String[] strings) {
		Map<String, Integer> map = new TreeMap();
		for (int i = 0; i < strings.length; i++) {
			String test = strings[i];
			if (map.containsKey(test)) {
				int count = map.get(test);
				map.put(test, count + 1);
			}

			else {
				map.put(test, 1);
			}
		}
		return map;
	}

}

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i fixed it. now i see sorted key output

--->{a=2, b=2, c=1}

gudii9

ASKER

package test;

import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;

public class WordCount {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		// wordCount(["a", "b", "a", "c", "b"]) → {"b": 2, "c": 1, "a": 2}
		// Map<String, String> map = new HashMap();
		// map.put("b", null);
		// map.put("a", "Hi");
		String[] arr = { "a","e","b", "a", "c", "b" };
		System.out.println("--->" + wordCount(arr));

	}

	/*
	 * private static String mapAB(String[] arr) { // TODO Auto-generated method
	 * stub return null; }
	 */

	public static Map<String, Integer> wordCount(String[] strings) {
		Map<String, Integer> map = new HashMap();
		for (int i = 0; i < strings.length; i++) {
			String test = strings[i];
			if (map.containsKey(test)) {
				int count = map.get(test);
				map.put(test, count + 1);
			}

			else {
				map.put(test, 1);
			}
		}
		return map;
	}

}

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even after changing TreeMap to HashMap back again why and how it is sorting?

--->{a=2, b=2, c=1, e=1}

gudii9

ASKER

public Map<String, Integer> wordCount(String[] strings) {
  Map<String, Integer> map=new TreeMap();
  for(int i=0;i<strings.length;i++){
  String test=strings[i];
  if(map.containsKey(test)){
  int count=map.get(test);
  map.put(test,count+1);
  }
  
  else{
  map.put(test,1);
  }
}
  return map;
}

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codingbat supported TreeMap as well