Counting occurence of a character from the console input stream

Question

In an interview I was asked a question like:

Take an input from console like: "welcome to world" and count a particular character entered by the user at which index and how many times(i.e. occurance of the character) without using any built-in methods like charAt(int ind) etc.

And your question is... – Luiggi Mendoza Oct 01 '13 at 05:31 — Luiggi Mendoza, Oct 01 '13 at 05:31
And what have you tried so far? – Subhrajyoti Majumder Oct 01 '13 at 05:31 — Subhrajyoti Majumder, Oct 01 '13 at 05:31
And did you get the job.? :P – user2339071 Oct 01 '13 at 05:34 — user2339071, Oct 01 '13 at 05:34

Rahul · Answer 1 · 2013-10-01T05:43:53.057

7

Giving you a potted answer won't help you at all. Here's how you can achieve what you want. Try to code it yourself.

Convert your String to a Character Array.
Have a Map which would store the char element as the key and its count as the value.
Iterate over the char array and for each element, check if its already existing in the map.
a. If it exists, increment the value for that element by 1 and put it back in the map.
b. If it doesn't, insert that char along with 1 as its count value in the map.
Continue till there are more elements in the char array.
The map now has all the char along with their respective counts.

edited Oct 01 '13 at 05:43

answered Oct 01 '13 at 05:35

Rahul

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Just one tip: use a `Map` instead of a `HashMap` directly. Refer to http://stackoverflow.com/q/383947/1065197 for more info regarding this topic – Luiggi Mendoza Oct 01 '13 at 05:42
1

@LuiggiMendoza - Suggestion taken! :) I went into the `java` mode when the Map came up, as I'm tuned to using the `Map map = new HashMap()` more often than not! – Rahul Oct 01 '13 at 05:45

score 0 · Answer 2 · edited Oct 01 '13 at 05:50

import java.io.Console;
class dev
{
    public static void main(String arg[])
    {
        Console c=System.console();
        String str=c.readLine();
        System.out.println(str);
        int times=0;
        //find c character 
        char find='c';
        char strChar[]=str.toCharArray();
        System.out.print("positions of char c in the string :");
        try
        {
            for (int i=0; ;i++ )
            {
                if(strChar[i]==find)
                {
                    System.out.print((i-1)+", ");times++;
                }
            }   
        }
        catch (Exception e)
        {
            System.out.println("\n"+"The no. of times c occur : "+times);
        }
    }
}

You're terminating your for-loop using an IndexOutOfBoundsException??? Bold choice! — Henrik Aasted Sørensen, Oct 01 '13 at 05:58

Counting occurence of a character from the console input stream

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