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We are going to write a Python program that reads from standard input and writes to standard output.
The problem is to process a string that might contain the word "PYTH" as a substring, but we have to replace every occurrence of "PYTH" with "PYTHON".
However, note that the problem says: "replace every occurrence of the substring 'PYTH' with 'PYTHON'".
But we must be cautious: what if the substring appears as part of a larger word? The problem does not specify word boundaries, so we replace every occurrence.
Example:
Input: "I love PYTH and PYTHON"
Output: "I love PYTHON and PYTHON"
Steps:
We can read the entire input as a string, then use the replace method to replace every occurrence of "PYTH" with "PYTHON".
However, note: what if we have overlapping occurrences? The replace method in Python does not handle overlapping by default, but the problem says "every occurrence".
Since the replacement string is longer, we have to be cautious of the order. Actually, the replace method in Python replaces non-overlapping occurrences from left to right.
Example:
s = "PYTHPYTH"
s.replace("PYTH", "PYTHON") -> replaces the first "PYTH" at index0, then the next occurrence starts at index4?
But after replacing the first, the string becomes "PYTHONPYTH", then the next occurrence is at index6?
So we get "PYTHONPYTHON".
But note: the problem says "every occurrence", and the example above does replace every occurrence.
However, what if we have an occurrence that is contained in the replacement?
Example: "PYTH" -> replaced by "PYTHON", which contains "PYTH" again?
But note: the replacement is done from left to right and the replacement does not re-scan the part that has been replaced.
So we can safely use the replace method.
Steps in code:
Read the entire input from stdin.
Replace every occurrence of "PYTH" with "PYTHON".
Print the result.
Let's code accordingly.
To solve this problem, we need to replace every occurrence of the substring "PYTH" with "PYTHON" in the input string. The solution involves reading the input, performing the replacement, and then outputting the modified string.
Approach
Read Input: The input is read from standard input as a single string.
Replace Substring: Using Python's built-in string method replace(), we replace every occurrence of "PYTH" with "PYTHON". This method efficiently handles all non-overlapping occurrences from left to right.
Output Result: The modified string is then printed to standard output.
This approach ensures that all instances of "PYTH" are replaced, regardless of their position in the string, and handles overlapping occurrences correctly by processing the string from left to right without re-scanning replaced parts.
Solution Code
import sys
def main():
data = sys.stdin.read()
result = data.replace("PYTH", "PYTHON")
print(result)
if __name__ == "__main__":
main()
Explanation
Reading Input: The sys.stdin.read() function reads the entire input from standard input until an EOF (End of File) is encountered. This allows processing multi-line inputs seamlessly.
Replacing Substrings: The replace() method is called on the input string to replace every occurrence of "PYTH" with "PYTHON". This method processes the string in a single pass, ensuring efficiency and correctness.
Output: The modified string is printed to standard output, which can be redirected to a file or another process as needed.
This solution efficiently handles all edge cases, including overlapping substrings, by leveraging Python's robust string handling capabilities. The approach is both concise and optimal for the given problem.
Okay, so I need to solve this problem where I have to find the value of ( y ) given the equation ( y = \sqrt{5x^2 + 3} ) when ( x = 2 ). Let me think through this step by step.
First, the equation is already solved for ( y ), which is good. That means I can plug in the value of ( x ) directly. The value of ( x ) given is 2. So, I need to substitute 2 into the equation wherever there's an ( x ).
Let me write that out. The original equation is ( y = \sqrt{5x^2 + 3} ). Substituting ( x = 2 ), it becomes ( y = \sqrt{5*(2)^2 + 3} ). Wait, let me make sure I do the order of operations correctly here. According to PEMDAS—Parentheses, Exponents, Multiplication and Division, Addition and Subtraction—I should handle the exponent first, then multiplication, and finally addition inside the square root.
So, starting inside the square root: ( 5x^2 ). Since ( x = 2 ), that becomes ( 5*(2)^2 ). The exponent here is ( 2^2 ), which is 4. Then multiply by 5: 5*4 = 20. Then add 3, so 20 + 3 = 23. Therefore, the equation simplifies to ( y = \sqrt{23} ).
Wait, is that right? Let me check again. If ( x = 2 ), then ( x^2 = 4 ). Multiply by 5: 5*4 is indeed 20. Then add 3: 20 + 3 = 23. So the square root of 23 is ( y ). Hmm, but is there a simpler form for ( \sqrt{23} )? Let me see. 23 is a prime number, right? So it doesn't have any perfect square factors other than 1. Therefore, ( \sqrt{23} ) is already in its simplest radical form. So that should be the answer.
But just to make sure I didn't make any mistakes, let me go through each step again. Substitute x = 2 into ( 5x^2 + 3 ). So, 5*(2)^2. 2 squared is 4, multiplied by 5 gives 20. Then add 3, getting 23. Square root of 23. Yep, that seems correct.
Alternatively, maybe I can verify by calculating the decimal value to check if it makes sense. Let's see, ( \sqrt{23} ) is approximately 4.7958. Let me check with another method. If I compute 5*(2)^2 + 3, that's 5*4 + 3 = 20 + 3 = 23. Square root of 23 is indeed approximately 4.7958. So that seems reasonable.
Wait, but maybe the problem expects an exact value rather than a decimal approximation. Since the question says "find the value of ( y )", and unless specified otherwise, leaving it in the radical form is probably better. So ( \sqrt{23} ) is the exact value, and that's the answer they want.
Is there any chance I misread the original equation? Let me check again. The equation is ( y = \sqrt{5x^2 + 3} ). Yes, that's correct. And substituting x = 2. No, that's right. So, I think I did everything correctly.
Another way to think about it: Maybe expand the equation step by step. Let's see:
Start with ( y = \sqrt{5x^2 + 3} ).
Substitute x = 2:
( y = \sqrt{5*(2)^2 + 3} ).
Calculate exponent first:
( 2^2 = 4 ).
Multiply by 5:
( 5*4 = 20 ).
Add 3:
( 20 + 3 = 23 ).
Take the square root:
( \sqrt{23} ).
Yes, that's consistent. So, unless there's a trick or something I'm missing here, the answer should be ( \sqrt{23} ). Maybe the problem is testing substitution into a radical equation. It seems straightforward, but sometimes problems have hidden steps. Let me check if there's any restriction on the value of y. Since it's a square root, the expression inside must be non-negative. But when x = 2, 5*(2)^2 + 3 = 23, which is positive, so no problem there. So y is a real number, specifically the positive square root of 23.
Alternatively, if the equation was different, like if there was a variable outside the square root or something, but in this case, it's straightforward. So I think I'm confident that ( y = \sqrt{23} ) is the correct answer.
Wait, but maybe the question expects a numerical approximation? The original problem didn't specify. But since it's presented in a mathematical notation with the square root, it's more likely they want the exact value. So, sticking with ( \sqrt{23} ) is the way to go.
Just to recap:
Substitute x = 2 into the equation.
Calculate the exponent first: 2 squared is 4.
Multiply by 5: 5*4 = 20.
Add 3: 20 + 3 = 23.
Take the square root of 23.
Since 23 is prime, the square root can't be simplified further.
Therefore, the value of y is ( \sqrt{23} ).
I don't see any mistakes in this process. Each step follows the order of operations, and the substitution is done correctly. So I think that's the final answer.
To find the value of ( y ) when ( x = 2 ) in the equation ( y = \sqrt{5x^2 + 3} ):
Substitute ( x = 2 ) into the equation:
[
y = \sqrt{5(2)^2 + 3}
]
Calculate the exponent:
[
2^2 = 4
]
Multiply by 5:
[
5 \times 4 = 20
]
Add 3:
[
20 + 3 = 23
]
Take the square root:
[
y = \sqrt{23}
]
Since 23 is a prime number, (\sqrt{23}) cannot be simplified further.
Answer: (\boxed{\sqrt{23}})
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发表于 2025-11-3 23:53:27