The challenge
Complete the solution so that it splits the string into pairs of two characters. If the string contains an odd number of characters then it should replace the missing second character of the final pair with an underscore (‘_’).
Examples:
StringSplit.solution("abc") // should return {"ab", "c_"}
StringSplit.solution("abcdef") // should return {"ab", "cd", "ef"}
Test cases
import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;
import java.util.Arrays;
public class SampleTest {
@Test
public void testEvenString() {
String s = "abcdef";
String s1 = "HelloWorld";
assertEquals("Should handle even string","[ab, cd, ef]", Arrays.toString(StringSplit.solution(s)));
assertEquals("Should handle even string","[He, ll, oW, or, ld]", Arrays.toString(StringSplit.solution(s1)));
}
@Test
public void testOddString() {
String s = "abcde";
String s1 = "LovePizza";
assertEquals("Should handle odd string","[ab, cd, e_]", Arrays.toString(StringSplit.solution(s)));
assertEquals("Should handle odd string","[Lo, ve, Pi, zz, a_]", Arrays.toString(StringSplit.solution(s1)));
}
@Test
public void testEmptyString() {
String s = "";
assertEquals("Should handle empty string","[]", Arrays.toString(StringSplit.solution(s)));
}
}
The solution in Java
public class StringSplit {
public static String[] solution(String s) {
// if it's blank, then return
if (s.length()==0) return new String[0];
// if not even, then add an underscore to the end
if (s.length()%2!=0) {
s+="_";
}
// determine the space needed for the return array
int spaceNeeded = s.length()/2;
// create a new array to populate and return
String[] out = new String[spaceNeeded];
// create an builder index
int j = 0;
// loop through the input string
for (int i=0; i<s.length(); i++) {
// create a new string to build
StringBuilder sb = new StringBuilder();
// add the current item
sb.append(s.charAt(i));
// add the next item
sb.append(s.charAt(i+1));
// populate our output string as we go
out[j] = sb.toString();
// increment both counters
i++;
j++;
}
// return the built string
return out;
}
}
A simple alternative using regular expressions:
public class StringSplit {
public static String[] solution(String s) {
s = (s.length() % 2 == 0)?s:s+"_";
return s.split("(?<=\\G.{2})");
}
}
Another short regular expression solution:
class StringSplit {
static String[] solution(String s) {
return (s + (s.length() % 2 > 0 ? "_" : "")).split("(?<=\\G.{2})");
}
}
