String Traversal

All 15 string traversal questions

Work through the interactive quiz above first. This is the full string traversal question set with worked solutions, so students can review any question after attempting it.

1. 1.Code Tracing 01 - String Traversal: track the final printed value.

   String word = "ALGORITHM";
   int count = 0;
   for (int i = 0; i < word.length(); i++) {
     char c = word.charAt(i);
     if (c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U') count++;
   }
   System.out.print(count);

   • 6
   • 9
   • 4
   • 3
   Show worked solution

   Correct answer: 3

   The loop inspects one character per pass and only advances the counter on vowels.

2. 2.Code Tracing 12 - String Traversal: follow the variable updates.

   String word = "PROGRAM";
   String out = "";
   for (int i = word.length() - 1; i >= 0; i--) {
     out += word.charAt(i);
   }
   System.out.print(out);

   • MARGORP
   • PROGRAM
   • ARGORP
   • ROGRAM
   Show worked solution

   Correct answer: MARGORP

   Starting at length() - 1 and counting down visits the characters in reverse order.

3. 3.Code Tracing 28 - String Traversal: trace the branch and loop path.

   String word = "METHODS";
   String out = "";
   for (int i = 1; i < word.length(); i += 2) {
     out += word.charAt(i);
   }
   System.out.print(out);

   • EHD
   • MTOS
   • METHODS
   • HD
   Show worked solution

   Correct answer: EHD

   Starting the index at 1 and stepping by 2 picks up the characters at odd positions only.

4. 4.Code Tracing 39 - String Traversal: watch the index changes.

   String word = "ARRAYS";
   char target = word.charAt(0);
   int count = 0;
   for (int i = 0; i < word.length(); i++) {
     if (word.charAt(i) == target) count++;
   }
   System.out.print(target + ":" + count);

   • A:1
   • A:2
   • A:3
   • 0:2
   Show worked solution

   Correct answer: A:2

   Comparing char values with == is correct. The first character always matches itself, so the count is at least 1.

5. 5.Code Tracing 50 - String Traversal: evaluate the state change step by step.

   String word = "CODING";
   String out = "";
   for (int i = 0; i < word.length(); i++) {
     char c = word.charAt(i);
     if (c == 'A' || c == 'E') continue;
     out += c;
   }
   System.out.print(out);

   • The code does not compile.
   • CODING
   • CODINGAE
   Show worked solution

   Correct answer: CODING

   continue skips the append for the matching characters, so they are filtered out of the result.

6. 6.What is printed by the following code segment?

   String s = "mississippi";
   int c = 0;
   for (int i = 0; i < s.length() - 1; i++)
   {
       if (s.charAt(i) == s.charAt(i + 1)) { c++; }
   }
   System.out.print(c);

   • 3
   • 4
   • 2
   • 11
   Show worked solution

   Correct answer: 3

   The doubled pairs are ss, ss, and pp.

7. 7.What is printed by the following code segment?

   String s = "abcdef";
   String out = "";
   for (int i = 0; i < s.length(); i++)
   {
       out = i % 2 == 0 ? out + s.charAt(i) : s.charAt(i) + out;
   }
   System.out.print(out);

   • abcdef
   • fdbace
   • acebdf
   • fdbeca
   Show worked solution

   Correct answer: fdbace

   Even positions are appended and odd positions are prepended, so the two halves grow in opposite directions.

8. 8.What is printed by the following code segment?

   String s = "Hello World";
   int u = 0;
   for (int i = 0; i < s.length(); i++)
   {
       char c = s.charAt(i);
       if (c >= 'A' && c <= 'Z') { u++; }
   }
   System.out.print(u);

   • 10
   • 11
   • 2
   • 1
   Show worked solution

   Correct answer: 2

   Comparing a char against a range of letters works because char values are ordered, and two capitals appear.

9. 9.What is printed by the following code segment?

   String s = "abcba";
   boolean p = true;
   int i = 0;
   int j = s.length() - 1;
   while (i < j)
   {
       if (s.charAt(i) != s.charAt(j)) { p = false; }
       i++;
       j--;
   }
   System.out.print(p);

   • false
   • 5
   • The code does not compile.
   • true
   Show worked solution

   Correct answer: true

   Two indexes converge from the ends and every mirrored pair matches.

10. 10.What is printed by the following code segment?

    String s = "a1b2c3";
    int sum = 0;
    for (int i = 0; i < s.length(); i++)
    {
        char c = s.charAt(i);
        if (c >= '0' && c <= '9') { sum += c - '0'; }
    }
    System.out.print(sum);

    • 6
    • 150
    • 3
    • 0
    Show worked solution

    Correct answer: 6

    Subtracting the character zero converts a digit character to its numeric value, and 1, 2, and 3 total 6.

11. 11.What is printed by the following code segment?

    String s = "aabbaa";
    String out = "";
    for (int i = 0; i < s.length(); i++)
    {
        if (i == 0 || s.charAt(i) != s.charAt(i - 1))
        {
            out += s.charAt(i);
        }
    }
    System.out.print(out);

    • aabbaa
    • aba
    • ab
    • abab
    Show worked solution

    Correct answer: aba

    Only the first character of each run survives, which collapses consecutive duplicates.

12. 12.What is printed by the following code segment?

    String s = "abc";
    String out = "";
    for (int i = 0; i < s.length(); i++)
    {
        for (int j = i; j < s.length(); j++)
        {
            out += s.substring(i, j + 1) + " ";
        }
    }
    System.out.print(out.length());

    • 12
    • 10
    • 16
    • 18
    Show worked solution

    Correct answer: 16

    The six substrings have lengths 1, 2, 3, 1, 2, and 1, totalling 10, and each is followed by a space.

13. 13.What is printed by the following code segment?

    String s = "programming";
    int c = 0;
    for (int i = 0; i < s.length(); i++)
    {
        if ("aeiou".indexOf(s.charAt(i)) >= 0) { c++; }
    }
    System.out.print(c);

    • 4
    • 2
    • 11
    • 3
    Show worked solution

    Correct answer: 3

    The vowels present are o, a, and i.

14. 14.What is printed by the following code segment?

    String s = "abcd";
    String out = "";
    for (int i = s.length(); i > 0; i--)
    {
        out += s.substring(i - 1, i);
    }
    System.out.print(out);

    • dcba
    • abcd
    • dcb
    • abc
    Show worked solution

    Correct answer: dcba

    The loop counts down and takes one character at a time from the end.

15. 15.What is printed by the following code segment?

    String s = "the quick fox";
    int longest = 0;
    int run = 0;
    for (int i = 0; i < s.length(); i++)
    {
        run = s.charAt(i) == ' ' ? 0 : run + 1;
        if (run > longest) { longest = run; }
    }
    System.out.print(longest);

    • 3
    • 5
    • 13
    • 4
    Show worked solution

    Correct answer: 5

    The longest word is quick, with five characters.