CC-16 : Find most common response option selected.

Description:

Given a String 2d matrix named resps with responses to a survey across multiple days (each row has responses for a particular day), find the most common response option selected across days. If the same response repeats on the same day, it will be counted as one response option only.

Test cases and expected outputs:

Input Parameters	Expected outputs
resp={ {"yes","no","no","yes","yes"}, {"maybe","yes"}, {"maybe","no","no","yes","maybe","never"}}	Most common response option : yes
resp={ {"yes","no","no","yes","yes"}, {"maybe"}, {"maybe","no","no","maybe","never"}}	Most common response option : maybe,no

Pseudocode:

The java method should accept following input parameters: resps[][](String 2d matrix).

Initialize a variable idvRespMap of type HashMap to hold an individual days selected response options as keys, and the frequency of these selected options as the values.

Initialize a variable allRespMap of type HashMap to hold all days response selected options as keys, and the frequency of these selected options as the values.

Initialize an ArrayList< String> mostCommResp to hold most common selected response options.

Initialize an integer variable mostCommRespCnt to 0.

Iterate through resps using a for loop with allResp as a loop variable with initial value 0 and increment allResp till it reaches resps.length-1:

Clear entries in idvRespMap, as for each individual days responses, we want to start with an empty idvRespMap.

Iterate through resps using a for loop with idvResp as a loop variable with initial value 0 and increment idvResp till it reaches resps[allResp].length-1:

If idvRespMap does not contain key resps[allResp][ idvResp], then:

Put key-value pair resps[allResp][ idvResp]and 1 to idvRespMap.

If allRespMap contains key resps[allResp][ idvResp]with value freq, then put key-value pair resps[allResp][ idvResp] and freq+1 to allRespMap.

If allRespMap.get(resps[allResp][ idvResp]) > mostCommRespCnt:

Set mostCommRespCnt to allRespMap.get(resps[allResp][ idvResp]).

Remove all existing entries from mostCommResp as we have found a new higher mostCommRespCnt.

Add resps[allResp][ idvResp] to mostCommonResps.

Else:

 If allRespMap.get(resps[allResp][ idvResp]) == mostCommRespCnt, then Add resps[allResp][ idvResp] to mostCommonResps, as we have found a duplicate most common response option.

After above loop completes, mostCommonResps contains the most common response option selected across days. Return mostCommonResps.toArray().

Code:

public String[] hashMapFindMostCommonResponse(String[][] resps) throws Exception{
	HashMap<String,Integer> idvRespMap=new HashMap<String, Integer>();
	HashMap<String,Integer> allRespMap=new HashMap<String, Integer>();
	ArrayList<String> mostCommResp=new ArrayList<String>(); 
	int mostCommRespCnt=0;
	for (int allResp=0; allResp < resps.length; allResp++) {
		idvRespMap.clear();
		for (int idvResp=0; idvResp < resps[allResp].length; idvResp++) {
			if (!idvRespMap.containsKey(resps[allResp][idvResp])) {
				idvRespMap.put(resps[allResp][idvResp],1);
				allRespMap.put(resps[allResp][idvResp], allRespMap.getOrDefault(resps[allResp][idvResp], 0)+1);			
				if (allRespMap.get(resps[allResp][idvResp]) > mostCommRespCnt) {
					mostCommRespCnt=allRespMap.get(resps[allResp][idvResp]);
					mostCommResp.clear();
					mostCommResp.add(resps[allResp][idvResp]);
				}else {
					if (allRespMap.get(resps[allResp][idvResp]) == mostCommRespCnt) {
					mostCommResp.add(resps[allResp][idvResp]);
					}
				}
			}
		}		
	}		
	return 	mostCommResp.toArray(new String[0]);
}

Click here to download and run code and test cases !

Below fully running code can be copied and run on Eclipse or other Java IDEs. Refer the classname in code below. If the class name below is "A", save the code below to a file named A.java before running it. Be sure to try your own test cases to enhance your understanding ! You can also tweak the code to optimize or add enhancements and custom features.

import java.util.ArrayList;
import java.util.HashMap;


public class HashMapFindMostCommonResponse {
	
public String[] hashMapFindMostCommonResponse(String[][] resps) throws Exception{
	HashMap<String,Integer> idvRespMap=new HashMap<String, Integer>();
	HashMap<String,Integer> allRespMap=new HashMap<String, Integer>();
	ArrayList<String> mostCommResp=new ArrayList<String>(); 
	int mostCommRespCnt=0;
	for (int allResp=0; allResp < resps.length; allResp++) {
		idvRespMap.clear();
		for (int idvResp=0; idvResp < resps[allResp].length; idvResp++) {
			if (!idvRespMap.containsKey(resps[allResp][idvResp])) {
				idvRespMap.put(resps[allResp][idvResp],1);
				allRespMap.put(resps[allResp][idvResp], allRespMap.getOrDefault(resps[allResp][idvResp], 0)+1);			
				if (allRespMap.get(resps[allResp][idvResp]) > mostCommRespCnt) {
					mostCommRespCnt=allRespMap.get(resps[allResp][idvResp]);
					mostCommResp.clear();
					mostCommResp.add(resps[allResp][idvResp]);
				}else {
					if (allRespMap.get(resps[allResp][idvResp]) == mostCommRespCnt) {
					mostCommResp.add(resps[allResp][idvResp]);
					}
				}
			}
		}		
	}		
	return 	mostCommResp.toArray(new String[0]);
}
	
	
    
public static void main(String[] args) {
	
	HashMapFindMostCommonResponse hp=new HashMapFindMostCommonResponse();
	String[] retVal;
	try {
	String[][] resp={		{"yes","no","no","yes","yes"},
							{"maybe","yes"},
							{"maybe","no","no","yes","maybe","never"},
	};
	print2dArray(resp, "Files list");
	retVal=hp.hashMapFindMostCommonResponse(resp);
	printArraySummary(retVal, "Most common responses");
			
	String[][] resp1={		{"yes","no","no","yes","yes"},
							{"maybe"},
							{"maybe","no","no","maybe","never"},
	};
	print2dArray(resp1, "Files list");
	retVal=hp.hashMapFindMostCommonResponse(resp1);
	printArraySummary(retVal, "Most common responses");
		
			
	}catch (Exception exception) {
	System.out.print("Exception: "+ exception);
	exception.printStackTrace();
	}
				
}

public static void print2dArray(String[][] sArray, String label) throws Exception {
	// Case 1: The input Array is null !!
    if (sArray == null) { System.out.println("\n\n Input 2d Array was null !! \n"); return; }
    // Case 2: Print input Array by index (first to last)
	System.out.println();
	System.out.println("******************************************************************************");
	System.out.print(label+" : \n");
	int rIdx=0; int cIdx=0;
	for (rIdx=0; rIdx < sArray.length; rIdx++) {
		for (cIdx=0; cIdx < sArray[rIdx].length; cIdx++) {
			System.out.print(sArray[rIdx][cIdx]);
			if (cIdx < sArray[rIdx].length) System.out.print(",");
		}
		System.out.print("\n");
	} 
	System.out.println();
	System.out.println("******************************************************************************");
	System.out.println();
	Thread.sleep(2000);
	return;
}


public static void printArraySummary(String[] intArray, String label) throws Exception {
   	// Case 1: The input Array is null !!
	if (intArray == null) { System.out.println("\n\n Input Array was null !! \n"); return; }
	// Case 2: Print input Array by index (first to last)
	System.out.println();
	System.out.println("************************************************************************");
	System.out.print(label+" : ");
	int arrayIndex=0;
	for (arrayIndex=0; arrayIndex< intArray.length; arrayIndex++) {
			System.out.print(intArray[arrayIndex]);
			if (arrayIndex< intArray.length-1) {System.out.print(",");}
	} 
	System.out.println();
	System.out.println("*************************************************************************");
	System.out.println();
	Thread.sleep(2000);
	return;
}

}