public class Solution {

  public String removeSpaces(String input) {

    // Write your solution here

    int i = 0;

    int slow = 0;

    int count = 0;

    int len = input.length();

    char[] charArr = input.toCharArray();

    while(true) {

      while (i < len && charArr[i] == ' ') {

        i += 1;

      }

      if (i == len) {

        break;

      }

      if (count > 0) {

        charArr[slow++] = ' ';

      }

      while (i < len && charArr[i] != ' ') {

        charArr[slow++] = charArr[i++];

      }

      count += 1;

    }

    return new String(charArr, 0, slow);

  }

}

public class Solution {

  public String removeSpaces(String input) {

    // Write your solution here

    int slow = 0;

    char[] charArr = input.toCharArray();

    for (int i = 0; i < charArr.length; i++) {

      if (charArr[i] == ' ' && (i == 0 || charArr[i - 1] == ' ')) {

        continue;

      }

      charArr[slow++] = charArr[i];

    }

    if (slow > 0 && charArr[slow - 1] == ' ') {

      return new String(charArr, 0, slow - 1);

    }

    return new String(charArr, 0, slow);

  }

}