Odtnhj

It is an interview question. The input is an ArrayList. My first idea is to convert it into a 2D matrix and then combine each column, but it seem like not the right answer. Is there any other way to solve this? Thanks.

Input

"abc", 
"bef", 
"g"

Expected Output (first column, abg, then the second column, be and finally the third column, cf):

"abgbecf"

Something like this would work:

StringBuilder sb = new StringBuilder()
int max = 0;
for(String str : arrList)
 if(str.length > max) 
 max = str.length;
 

for(int i = 0; i < max; i++)
 for(String str : arrList)
 if(str.length > i)
 sb.append(str.charAt(i));
 
 

return sb.toString();

I think I would simply loop through the list pulling the next character out of the original strings and adding it to the new combined string, until the last letter of the longest string was added.

boolean keepGoing = true;
int index = 0;
StringBuilder result = new StringBuilder();
while(keepGoing) 
 keepGoing = false;
 for(int i=0; i < stringList.size(); i++) 
 if(stringList.get(i).length() > index) 
 result.append(stringList.get(i).charAt(index));
 keepGoing = true;
 
 
 index++;

System.out.println("result: " + result);

There are probably more elegant solutions, but this is what I would start with and then refine as needed.

An easy way would be to use a StringBuilder:

StringBuilder sb = new StringBuilder()
for(String str : arrList)
 sb.append(str)

return sb.toString()