从Java中的字符串中删除相邻的重复项

Question

Let's say I have an input String as "aaabbaccd". I need to design a program which remove all the adjacent duplicates from my output. So taking the example of above string, the output would be : 1. First output that I would get after removing adjacent duplicates would be "aad" (Removed aabbcc from my input). 2. In the second pass, it would remove aa from my string and make my output as "d".

So far, what I could design the below code :

String input="aaabbaccd";

    String[] arr=input.split("");

    int n=arr.length;
    for(int i=0;i<n;i++) {
        if(i==arr.length-1) {
            if(arr[i-1].equals(arr[i])) {
                break;
            }
            else {
                System.out.print(arr[i]+ "");
                break;
            }
        }
        if(arr[i].equals(arr[i+1])) {
            i=i+1;
            continue;
        }
        if(!arr[i].equals(arr[i+1])) {
            System.out.print(arr[i]+ "");
        }
    }

The problem with this code is that it gives me output as aad. I cannot comprehend how to do the second pass on my code. Maybe recursion is something that I need to implement in this code. Please help me how to implement recursion in this code.

Answer 1

One lazy alternative is to use regexp for it, where the (.) part matches any character and saving it, and the \\\\1 references back to that match. I have added recursion to continue to apply the removal until string is no longer modified:

public String removeDuplicates(String original)
{
    String reduced = original.replaceAll("(.)\\1", "");

    if(reduced.equals(original))
        // No more duplicates, return original string
        return original;
    else
        // Duplicates were removed, continue recursion...
        return removeDuplicates(reduced);
}

The behaviour is verified with:

@Test
public void testIt()
{
    assertThat(removeDuplicates("aaabbaccd"), is("d"));
}

Answer 2

public static void main(String[] args) {
        String input="aaabbaccd";
        removeDupe(input);


    }

    public static void removeDupe(String input) {
        String[] arr=input.split("");

        StringBuffer sb=new StringBuffer();
        int n=arr.length;
        for(int i=0;i<n;i++) {
            if(i==arr.length-1) {
                if(arr.length==1) {
                    sb.append(arr[i]);
                    break;
                }
                if(arr[i-1].equals(arr[i])) {
                    break;
                }
                else {
                    sb.append(arr[i]);
                    break;
                }
            }
            if(arr[i].equals(arr[i+1])) {
                i=i+1;
                continue;
            }
            if(!arr[i].equals(arr[i+1])) {
                sb.append(arr[i]);
            }
        }

        //System.out.println(sb);

        if(sb.toString().equals(input)) {
            System.out.println(sb);
        }
        else {
            removeDupe(sb.toString());
        }


    }

Answer 3

接下来的一支班轮怎么样？

(new LinkedHashSet<Character>("aaabbaccd".chars().mapToObj(i -> (char)i).collect(Collectors.toList()))).stream().map(e -> e.toString()).collect(Collectors.joining());

Answer 4

I used StringBuilder class to store string and used StringBuilder's replace() method to remove Adjacent char.

This statement: str.replace(i,i+2,"") will actually delete adjacent chars.

The core logic is written in a static method named remove() . Note the point that I called the remove() method more than once ie str.length()/2 times. Because to remove Adjacent pair in new string we got after calling remove() each time.

public class RemoveDupl12{           
 public static StringBuilder remove(StringBuilder  str){    

   for( int i=0; i<str.length()-1; i++ )

    {
        if(str.charAt(i)==str.charAt(i+1))
        { 
            str.replace(i,i+2,"");
            i++;
        }
    }
    return str;
}

public static void main(String[] args) {
     StringBuilder str=new StringBuilder("daaabbad");

     for(int i=str.length()/2;i>0;i--)
     str=remove(str);

     if(str.length()==0)
         System.out.println("Final output=empty string"+str);

     else
         System.out.println("Final output="+str);
}}