CareerCup

public class Spaces {
    
    public List<String> getSpaces(String initial){
        String[] chars = initial.split("");
        List<String> charList = Arrays.asList(chars);
        List<String> pals = new ArrayList<String>();
        getCombinaciones(charList.get(1), charList, pals, 2);
        return pals;
    }

    private void getCombinaciones(String curString, List<String> charList, List<String> pals, int i) {
        if(i >= charList.size()){
             pals.add(curString);
        }else{
           getCombinaciones(curString + "_" + charList.get(i), charList, pals, i+1);
           getCombinaciones(curString + "" + charList.get(i), charList, pals, i+1);
        }
    }
    
    public static void main(String[] args) {
        Spaces program = new Spaces();
        List<String> comb = program.getSpaces("abcd");
        
        for (String string : comb) {
            System.out.println(string);
        }
    }

is a_bc_d is valid along with a_b_cd, ab_cd and ab_c_d ?

#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <bitset>

using namespace std;

string insert_spaces(string x, string y){
	int i;
	string result;
	for(i=0;i<x.length();i++){
		result += x[i];
		if(y[i]!='0'){
			result += "_";
		}
	}
	return result;
}
int main(){
	int i;
	string bitcode;
	for(i=0;i<8;i++){
		bitset<3> x(i);
		bitcode = x.to_string();
		bitcode += '0'; 
		cout << insert_spaces("abcd",bitcode) << endl;
	}
}

#include <iostream>
#include <string>
#include <list>
#include <conio.h>

using namespace std;

list<string> insert_spaces(string str)
{
    list<string> result;
    string temp;
    for(unsigned int i = 1; i < 2 << str.size() - 2; i++)
    {
        int f = i, j = 1;
		temp = str;
        while(f != 0)
        {
            if(f % 2 == 1)
				temp.insert(j++, "_");
            f /= 2;
			++j;
        }
        result.push_back(temp);
        temp.clear();
    }
    return result;
}

int main()
{
    list<string> string_list = insert_spaces("abcd");
    for( list<string>::iterator i = string_list.begin(); i != string_list.end(); i++)
    {
        cout << *i << endl;
    }
	_getch();
    return 0;
}

it returns all the string combinations in form of array.

public static string[] string_combinations(string s)
        {
            //points to main array index
            int index = 0;
            //Create an array length of n(n+1)/2
            string[] combiArray = new string[(s.Length * (s.Length + 1))/2];
            combiArray[index++] = s;
            for (int i = 1; i < s.Length; i++)
            {    
                //recursive call on remaining string 
                //eg: if s = abcd and i = 1 recursive call of (bcd)
                //i = 2 recursive call of (cd)
                //i = 3 recursive call of (d)
                string[] subCombinations = string_combinations(s.Substring(i));                                   
                foreach (string item in subCombinations)
                {
                    if(item != null)
                        combiArray[index++] = s.Substring(0,i) + "_" + item;                                        
                }                                                                
            }
            return combiArray;
        }