在字符串中逐字逆序

Question

I am trying to reverse the words in a string word by word. But I am running into a bit of trouble. I know many people have used StringBuilder to do this problem but I wanted to try it out without it.

Input:

Hi there

Output:

iH ereht

Currently, my input string stops at the last word. I assume this is due to the fact that in my code, the reverse portion of the code only reverses when a ' ' or space is detected. I changed this by performing the reverse portion when the end of the string has been reached as well. ( i == len ) However this does not seem to fix the problem. I assume there is some logic error inside my if , else if statements and for loop as well. I was wondering if anyone could guide me in the right direction.

The test case string that I've been working on is

"Hi there Mr.Doge!"

The output I get right now is

iH ereht <-- space at the end of the string.

I printed some text as the code proceeds and the last word ( Mr.Doge! ) is being stored into temp but it is not being reverse.

Here is the output when I compile the code:

0
H
1
Hi
2
i
iH
3
t
4
th
5
the
6
ther
7
there
8
iH e
iH er
iH ere
iH ereh
iH ereht
9
M
10
Mr
11
Mr.
12
Mr.D
13
Mr.Do
14
Mr.Dog
15
Mr.Doge
16
Mr.Doge!
iH ereht 

My code:

public static String reverseWord(String str){
    int len = str.length();
    String reverse = "", temp = "";

    for (int i = 0; i < len; i++) {
        System.out.println(i);
        if (str.charAt(i) != ' '){
            temp += str.charAt(i);
            System.out.println(temp);
        }
        else if (str.charAt(i) == ' ' || i == len){
        //if (str.charAt(i) == ' ') {
            for (int j = temp.length() - 1; j >= 0; j--) {      // reverse
                reverse += temp.charAt(j);                      // append in reverse
                System.out.println(reverse);
            }
            reverse += ' ';
            temp = "";
        }
    }
    return reverse;
}

Answer 1

With a couple of modifications this must work. See comments in code, to see what I modified.

Code:

public static void main(String[] args)
{
    System.out.println(reverseWord("Hello world Liondancer"));
}

public static String reverseWord(String str)
{
    int len = str.length();
    String reverse = "", temp = "";

    for (int i = 0; i < len; i++) {   // i == len comparison is unuseful since 'i' won't never be 'len'
        if (str.charAt(i) != ' ') {
            temp = str.charAt(i) + temp; // What you did, but add the current character first, THIS IS THE REVERSE!!!
        } else if (str.charAt(i) == ' ') {
            reverse += temp + " ";
            temp = "";
        }
    }
    reverse += temp; // Added this outside the loop to add last word stored in 'temp'
    return reverse;
}

Output:

olleH dlrow recnadnoiL

Note:

I deleted the nested for since it is not necessary.

Answer 2

try this change

    for (char c : str.toCharArray()) {
        if (c != ' '){
            temp = c + temp;
        } else {
            reverse += temp + ' ';
            temp = "";
        }
    }
    reverse += temp;

Answer 3

Reverse outside your loop and check that you're not at the last word (like so) -

public static String reverseWord(String str) {
  int len = str.length();
  String reverse = "", temp = " ";

  for (int i = 0; i < len; i++) {
    if (str.charAt(i) != ' ') {
      temp += str.charAt(i);
    } else if (str.charAt(i) == ' ' || i == len) {
      if (i + 1 < len) {
        for (int j = temp.length() - 1; j >= 0; j--) { // reverse
          reverse += temp.charAt(j); // append in reverse
        }
        temp = " ";
      } else {
        temp = "";
      }
    }
  }
  for (int j = temp.length() - 1; j >= 0; j--) { // reverse
    reverse += temp.charAt(j); // append in reverse
  }
  return reverse;
}

Answer 4

If i were to do it I would just store entire string in an arraylist. then say:

for(i=0;i<len;i++)
    temp.size()=len;
    temp(length-i)=str(i);
    print temp;

Answer 5

You can use the loop in this way too...

   public String reverseString(String str){
       String reverse="";

       for(int i=str.length()-1; i>=0; i--){

           reverse = reverse + str.charAt(i);

       }
          return reverse;

   }