Find the Sequence of Strings Appeared on the Screen in Java

Java usually uses GUI elements like JLabel or System.out.println() to capture and track printed output in order to determine the string sequence that appeared on the screen. It can be accomplished by dynamically storing the sequence of printed strings by rerouting System.out to a ByteArrayOutputStream or logging framework. Event listeners are used in GUI applications to monitor text changes in UI elements. In debugging or competitive programming, keeping a list or queue to hold outputs guarantees accurate order tracking. Developers may effectively examine the precise order of displayed strings with this method, which is helpful for testing, debugging, and logging.

On her computer, Alice will use a unique keyboard with just two keys to enter the following:

Adding the letter "a" to the string on the screen is done with Key 1.

By pressing Key 2, the string's final character on the screen is changed to the next character in the English alphabet. As an example, "c" becomes "d" and "z" becomes "a".

Remarkably, she can only press key one at first since the screen displays an empty string "".

Using the fewest possible actions, return a list of every string that appears on the screen while Alice inputs the target in the specific order that they appear.

Example 1:

Input:

String target = "xyz"

Output:

The strings that appear on the screen is ["x", "xx", "xy", "xyz"].

Explanation:

User should press the following keys in order:

• The string that appears on the screen changes to "x" when you press key 1.
• The string that appears on the screen changes to "xx" when you press key 1.
• When we hit key 2, "xy" appears on the screen.
• When we hit key 3, "xyz" appears on the screen.

Example 2:

Input:

String str = "hello"

Output:

The strings that appear on the screen is ["a", "b", "c", ..., "h",

"ha", "hb", "hc", ..., "he",

"hea", "heb", "hec", ..., "hel",

"hela", "helb", "helc", ..., "hell",

"hella", "hellb", "hellc", ..., "hello"]

Explanation:

• Press "a" → "a" appears on the screen.
• Increase the character one after the other until 'h' → Screen: "h"
• Include "a" → Screen: "ha"
• Raise 'a' to 'e' → Screen: "he"
• Expand 'a' until 'l' → Screen: "hel" and then add 'a' until "hea" appears.
• Add 'a' → Screen: "hela"
• Expand 'a' until 'l' → "hell" appears on the screen.
• Enter "a" → "hello" on the screen.
• Increase 'a' to 'o' → "hello" appears on the screen.

Example 3:

Input:

String str = "java"

Output:

The strings that appear on the screen is ["a", "b", "c", ..., "j",

"ja", "jb", "jc", ..., "ja",

"jaa", "jab", "jac", ..., "jav",

"java"]

Explanation:

• Press "a" → "a" appears on the screen.
• Characters are added one after the other till 'j' → Screen: "j".
• 'a' is added, and the screen displays "ja"
• Re-add "a" → Screen: "jaa"
• Raise 'a' to 'v' → Screen: "jav"
• Add 'a' → Screen: "java"

Approach: Brute Force

We must take an organized approach in order to create the string sequence that user can type. One key can be used to append a 'a' to an empty string, and another can be used to modify the final character to the subsequent character in the alphabet. Finding the shortest string sequence that leads to the target string is the aim.

Algorithm:

Step 1: Start with an empty string and use a StringBuilder to create the current string.

Step 2: All of the strings that show up on the screen should be stored in a list.

Step 3: 'a' should be appended to the current string for each character in the target string.

Step 4: To the list of answers, add the current string.

Step 5: Once 'a' has been appended, we must create every string that may be created by swapping the final character of each character from 'b' to the current character in the target string.

Step 6: Set the StringBuilder's last character to each character between 'b' and the current character using a loop, updating the string as we go.

Implementation:

Output:

 The strings that appear on the screen is[a, b, c, d, e, f, g, h, ha, hb, hc, hd, he, hea, heb, hec, hed, hee, hef, heg, heh, hei, hej, hek, hel, hela, helb, helc, held, hele, helf, helg, helh, heli, helj, helk, hell, hella, hellb, hellc, helld, helle, hellf, hellg, hellh, helli, hellj, hellk, helll, hellm, helln, hello]