interview problem 1

MrJohnSmith.java

package com.spencerdo.brain;

/**
 * Created by doyonghoon on 2015. 11. 7..
 */
public class MrJohnSmith {

  private static final String NAME = "Mr John Smith";

  private static final char[] whitespace = new char[]{'0', '2', '%'};

  public String getResult() {
    char[] s = createTestName(NAME).toCharArray();
    int k = 0, p = s.length - 1;
    for (int i = s.length - 1; i > 0; i--) {
      if (s[i] != ' ') {
        k = i;
        break;
      }
    }

    while (k >= 0) {
      if (s[k] != ' ') {
        s[p] = s[k];
        p--;
      } else {
        for (char c : whitespace) {
          s[p] = c;
          p--;
        }
      }
      k--;
    }

    return String.valueOf(s);
  }

  private String createTestName(String s) {
    int count = getCharacterCount(s, ' ');
    StringBuilder builder = new StringBuilder(s);
    for (int i = 0; i < count; i++) {
      builder.append(' ').append(' ');
    }
    return builder.toString();
  }

  private int getCharacterCount(String s, char target) {
    int count = 0;
    for (char c : s.toCharArray()) {
      if (c == target) {
        count++;
      }
    }
    return count;
  }
}