CareerCup

Java using stack:

import java.util.Stack;

public class RemoveRepetitive
{
    public static void printUnique(String input)
    {
        Stack<Character> stack = new Stack<>();
        for (int index = 0; index < input.length(); index++)
        {
            if (!stack.isEmpty() && stack.peek() == input.charAt(index))
            {
                continue;
            }
            else
            {
                stack.push(input.charAt(index));
            }
        }
        System.out.println(stack.toString());
    }

    public static void main(String[] args)
    {
        printUnique("abababaabbbaaaa");
    }
}

def compress(string):                                                           
    prev = None                                                                 
    cons = 1                                                                    
    compressed = ''                                                             
    for i in string:                                                            
        if prev:                                                                
            if prev == i:                                                       
                cons += 1                                                       
            else:                                                               
                compressed += prev+str(cons)                                    
                cons = 1                                                        
        prev = i                                                                
    compressed += prev+str(cons)                                                
                                                                                
    return compressed

Simple and effective Java solution using while loop:

public String charFrequency(String s) {
    String res = "";
    int ind = 0;
    while (ind < s.length()) {
        char cur = s.charAt(ind);
        int num = 1;
        while (ind < s.length() - 1 && cur == s.charAt(ind + 1)) {
            ind++;
            num++;
        }
        ind++;
        res += String.format("%s%s", cur, num);
    }
    return res;
}

Sorry, Ignore my last comment. It was my first answer in careercup. It was showing error message, so I have added comment in all lines.
Please use this one:

my $str = 'abababaabbbaaaaa';
# a1b1a1b1a1b1a2b3a5
my @str = split '', $str;

my $op = '';
my $cnt = 1;
for my $i (0 .. length($str)) {
    if ($str[$i] eq $str[$i+1]) {
      $cnt++;
    } else {
      $op .= $str[$i].$cnt;
      $cnt = 1; 
    }
}
print $op;

def compress(string):                                                           
    prev = None                                                                 
    cons = 1                                                                    
    compressed = ''                                                             
    for i in string:                                                            
        if prev:                                                                
            if prev == i:                                                       
                cons += 1                                                       
            else:                                                               
                compressed += prev+str(cons)                                    
                cons = 1                                                        
        prev = i                                                                
    compressed += prev+str(cons)                                                
                                                                                
    return compressed

Ruby

def compressed(input)
  reps = []
  input.chars.each do |c|
    if reps[-2] == c
      reps[-1] += 1
    else
      reps << c << 1
    end
  end 
  reps * ""
end

def compress(word):
dic_letter = {}
for letter in word:
if(dic_letter.get(letter) == None):
dic_letter[letter] = 0
else:
dic_letter[letter] = dic_letter[letter] + 1
return dic_letter

print compress("asdasdssss")

def compress(word):
	dic_letter = {}
	for letter in word:
		if(dic_letter.get(letter) == None):
			dic_letter[letter] = 0
		else:
			dic_letter[letter] = dic_letter[letter] + 1
	return dic_letter

print compress("asdasdssss")

Here is simple solution in perl:

my $str = 'abababaabbbaaaaa';

my @str = split '', $str;

my $op = '';

my $cnt = 1;

for my $i (0 .. length($str)) {

if ($str[$i] eq $str[$i+1]) {

$cnt++;

} else {

$op .= $str[$i].$cnt;

$cnt = 1;

}

}

print $op;

#include <iostream>
#include <stdlib.h>

#define ARRAY_LENGTH 26

using namespace std;

int charArray[ARRAY_LENGTH] = {0};

int Solve(char* pSouce);
int Print();
void Reset();


void Reset(){ for ( int i = 0; i< ARRAY_LENGTH;i++){ charArray[i] = 0; } }

int Print(){
cout << endl;
char ch = 'a';
for ( int i = 0; i< ARRAY_LENGTH;i++){ cout <<"[" << (char(ch + i)) <<"]:"<< charArray[i] << endl; }
}

int Solve(string pSource){
if ( pSource.length() == 0 ){ return 0; }
for(int i = 0; i< pSource.length();i++){ //Assuming input string is NULL terminated.
int index = 0;
index = abs(pSource.at(i) - 'a');

if ( charArray[index] != 0 ){
charArray[index] +=1;
} else {
charArray[index] = 1;
}
}
return 1;
}



int main(){
string inputStr;
int test_cases = 0;
cin >> test_cases;
for ( int i = 0; i< test_cases; i++){
cin >> inputStr;
cout <<inputStr.c_str();
Solve(inputStr);
Print();
Reset();
}
}

#include <iostream>
#include <stdlib.h>

#define ARRAY_LENGTH 26

using namespace std;

int charArray[ARRAY_LENGTH] = {0};

int Solve(char* pSouce);
int Print();
void Reset();


void Reset(){ for ( int i = 0; i< ARRAY_LENGTH;i++){ charArray[i] = 0; } }

int Print(){
	cout << endl;
	char ch = 'a';
	for ( int i = 0; i< ARRAY_LENGTH;i++){  cout <<"[" << (char(ch + i)) <<"]:"<< charArray[i] << endl; }
}

int Solve(string pSource){
	if ( pSource.length() == 0 ){  return 0; }
	for(int i = 0; i< pSource.length();i++){				//Assuming input string is NULL terminated.
		int index = 0;
		index = abs(pSource.at(i) - 'a');

		if ( charArray[index] != 0 ){
			charArray[index] +=1;
		} else {
			charArray[index] = 1;
		}
	}
	return 1;
}



int main(){
	string inputStr;
	int test_cases = 0;
	cin >> test_cases;
	for ( int i = 0; i< test_cases; i++){
		cin >> inputStr;
		cout <<inputStr.c_str();
		Solve(inputStr);
		Print();
		Reset();
	}
}

If required as follows
input: aabbbbaab;
output: abab



public class RemoveDuplicates {
public static void main(String[] args) {
RemoveDuplicates dup = new RemoveDuplicates();
System.out.println(dup.compress("aabbbbbaab", 1));
}

private String compress(String string, int i) {
// TODO Auto-generated method stub
int start = 0;
char c = string.charAt(start);
String result = "";
while(i < string.length()) {
if(string.charAt(i) == c) {
i++;
} else {
result += c;
c = string.charAt(i);
i++;
}
}
result += c;
return result;
}
}

public class RemoveDuplicates {
public static void main(String[] args) {
RemoveDuplicates dup = new RemoveDuplicates();
System.out.println(dup.compress("aabbbbbaab", 1));
}

private String compress(String string, int i) {
// TODO Auto-generated method stub
int start = 0;
char c = string.charAt(start);
String result = "";
while(i < string.length()) {
if(string.charAt(i) == c) {
i++;
} else {
result += c;
c = string.charAt(i);
i++;
}
}
result += c;
return result;
}
}

public class Repeat {
	public static void main (String args[]) {
		System.out.println(new Repeat().compress("abababaabbbaaaaa"));
	}
	public String compress(String string) {
		if (string.length() == 0)
			return "";
		return compress(string, string.charAt(0), 0);
	}
	private String compress(String string, char c, int count) {
		if (string.length() == 0)
			return c+""+count+"";
		if (string.charAt(0) == c) {
			return compress(string.substring(1), c, count + 1);
		}else{
			if (count == 0)
				return c+""+compress(string.substring(1));
			return c+""+count+compress(string);
		}
	}
}

public void charFrequency() {
		String s = "aabbbcaghgggfg fhggssssy";
		String res = "";
		int cons = 1, i=0;
		boolean flag = false;
		if(s.length()==0)
		{
			res="Invalid Input";
		}
		else
		{
			for(i=0;i<s.length()-1;i++)
			{
				if(s.charAt(i)==s.charAt(i+1))
				{
					cons++;
					flag = true;
				}
				else
				{
					if(flag)
					{
						res+=s.charAt(i)+String.valueOf(cons);
						flag = false;
					}
					else
					{
						res+=s.charAt(i)+String.valueOf(cons);
					}
					cons=1;
				}

			}
			res+=s.charAt(i)+String.valueOf(cons);
			System.out.println(res);
		}
	}