CF 102697026 - Competition Rules
This is an introductory input/output problem. The program receives one line containing the rules of a competition, and its only job is to print a fixed heading followed by exactly the same line of rules.
CF 102697026 - Competition Rules
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Solve time: 4m 35s
Verified: yes
Solution
Problem Understanding
This is an introductory input/output problem. The program receives one line containing the rules of a competition, and its only job is to print a fixed heading followed by exactly the same line of rules. The heading must be Competition Rules: and the original input must appear unchanged on the next line. The official statement confirms that the intended solution is simply to read the line and print the heading and the input on separate lines.
There is no numerical constraint that changes the algorithmic choice. If the input line contains (L) characters, reading it and writing it takes (O(L)) time because every input character has to be processed or emitted at least once. The memory usage is (O(L)) if the line is stored as a Python string. Since there is no large numeric parameter or nested structure, algorithms such as sorting, dynamic programming, graph traversal, or brute-force search have no role here.
The main edge case is an empty rules line. For example,
contains an empty string as the competition rules. The correct output is
Competition Rules:
A careless implementation that calls strip() and then assumes there must be visible text could accidentally change the input or omit the second line. The safest approach is to read the complete line and print it without modifying its contents.
Another easy mistake is changing whitespace inside the rules. For example, with
Use 2 spaces here.
the correct output is
Competition Rules:
Use 2 spaces here.
A solution that splits the input into words and joins them again could silently turn multiple spaces into one. There is no reason to parse the rules, so treating the entire line as opaque text avoids that problem.
Approaches
The most direct approach is to read the one input line and print the required heading followed by the line. There is no meaningful combinatorial brute-force algorithm for this problem because the output is completely determined by the input.
If we want to contrast this with a deliberately inefficient implementation, suppose we copied the input one character at a time into a growing Python string using repeated concatenation. For a line of length (L), the accumulated string could be copied after every append, giving roughly
[ 1 + 2 + 3 + \dots + L = \frac{L(L+1)}{2} ]
character-copy operations in the worst case. That is (O(L^2)), even though the task only requires reproducing (L) characters.
The observation that the input already contains exactly the text we need to print eliminates all transformation work. We can retain the whole line as one string and output it directly. The optimal solution consequently performs only linear work, which is also the natural lower bound because the output itself contains (L) input characters.
| Approach | Time Complexity | Space Complexity | Verdict |
|---|---|---|---|
| Repeated string construction | O(L²) | O(L) | Unnecessarily slow |
| Direct read and print | O(L) | O(L) | Accepted |
Algorithm Walkthrough
- Read the single line containing the competition rules. We keep the line as text rather than splitting it because every character, including spaces, belongs to the required output.
- Print the fixed string
Competition Rules:. This is independent of the input and always occupies the first output line. - Print the input line exactly as it was read. The newline already consumed by
readline()is removed before printing so thatprint()does not create an extra blank line.
Why it works
The input consists of exactly one rules line, and the required output consists of two lines: a fixed heading and that same rules line. The algorithm prints the fixed first line and then prints precisely the stored input text as the second line. Since no transformation is applied to the rules, every character that should be preserved remains unchanged, so the produced output matches the required format.
Python Solution
import sys
input = sys.stdin.readline
def solve():
rules = input().rstrip('\n')
print("Competition Rules:")
print(rules)
if __name__ == "__main__":
solve()
The call to input() reads the single rules line. Using rstrip('\n') removes only the line-ending character added by the input operation. This is more precise than using strip(), because strip() would also remove meaningful spaces at the beginning or end of the rules.
The first print() produces the fixed heading required by the problem. The second print() produces the rules on a separate line.
There is no integer conversion, indexing, sorting, or other algorithmic processing. Python integers and overflow are irrelevant because the input is plain text.
Worked Examples
The official sample contains the following rules line:
This is a competition rule
The execution can be summarized as follows.
| Step | rules |
Output |
|---|---|---|
| 1 | This is a competition rule |
|
| 2 | This is a competition rule |
Competition Rules: |
| 3 | This is a competition rule |
Competition Rules: followed by This is a competition rule |
The trace demonstrates that the input is not interpreted or modified. It is simply placed after the required heading.
A second example with repeated spaces is useful because it catches solutions that tokenize the input.
Input:
Rules contain extra spaces
The execution is:
| Step | rules |
Output |
|---|---|---|
| 1 | Rules contain extra spaces |
|
| 2 | Rules contain extra spaces |
Competition Rules: |
| 3 | Rules contain extra spaces |
Competition Rules: followed by Rules contain extra spaces |
The multiple spaces remain unchanged. This is exactly why the rules should be treated as one string rather than reconstructed from individual words.
Complexity Analysis
| Measure | Complexity | Explanation |
|---|---|---|
| Time | O(L) | Reading and printing the rules processes (L) characters |
| Space | O(L) | The complete rules line is stored in memory |
Here (L) is the length of the input line. The solution is effectively optimal because producing the output already requires writing all (L) characters from the rules. The problem has no larger structural constraint that could make this approach unsuitable.
Test Cases
# helper: run solution on input string, return output string
import sys
import io
def solve():
rules = input().rstrip('\n')
print("Competition Rules:")
print(rules)
def run(inp: str) -> str:
global input
old_stdin = sys.stdin
old_stdout = sys.stdout
sys.stdin = io.StringIO(inp)
sys.stdout = io.StringIO()
input = sys.stdin.readline
try:
solve()
return sys.stdout.getvalue()
finally:
sys.stdin = old_stdin
sys.stdout = old_stdout
# Provided sample
assert run("This is a competition rule\n") == (
"Competition Rules:\n"
"This is a competition rule\n"
), "sample 1"
# Empty rules line
assert run("\n") == (
"Competition Rules:\n"
"\n"
), "empty rules"
# Repeated spaces
assert run("Rules contain extra spaces\n") == (
"Competition Rules:\n"
"Rules contain extra spaces\n"
), "preserve spaces"
# Leading and trailing spaces
assert run(" padded rules \n") == (
"Competition Rules:\n"
" padded rules \n"
), "preserve boundary spaces"
# A longer single line
long_rules = "A" * 100000
assert run(long_rules + "\n") == (
"Competition Rules:\n" + long_rules + "\n"
), "large input line"
| Test input | Expected output | What it validates |
|---|---|---|
This is a competition rule |
Heading followed by the same text | Official sample |
| Empty line | Heading followed by an empty line | Minimum-size input |
Rules contain extra spaces |
Same spaces preserved | Avoiding tokenization |
padded rules |
Same leading and trailing spaces | Boundary whitespace |
100000 A characters |
Heading followed by all characters | Large input handling |
Edge Cases
An empty rules line is handled by rstrip('\n'), which produces the empty string. The algorithm then prints the heading and calls print(""), producing the required blank second line. For input
the output is
Competition Rules:
A line containing repeated internal spaces is preserved because the program never calls split(). For input
Rules contain extra spaces
the stored value remains Rules contain extra spaces, and the same sequence is printed. A solution based on words could incorrectly collapse those spaces.
Leading or trailing spaces are also preserved because the code removes only the newline character. With
padded rules
the output contains the two leading and two trailing spaces exactly as supplied. Calling strip() instead would silently remove them.
Finally, a very long input line does not change the algorithm. If the line has (L) characters, the program still performs (O(L)) work and stores (O(L)) characters, which is the appropriate cost for an output-copying problem.