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POBounds and whole numbers
 

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    <p>I'm going through Bjarne Stroustrup's "Programming Principles and Practice Using C++". I am on chapter 4, exercise 4.</p> <p>The excercise is as follows:</p> <blockquote> <p>Write a program to play a numbers guessing game. The user thinks of a number between 1 and 100 and your program asks questions to figure out what the number is (e.g. "Is the number you are thinking of less than 50?"). Your program should be able to identify the number after asking no more than seven questions. Hint: Use the &lt; and &lt;= operators and if-else constructs.</p> </blockquote> <p>Now that is great, and I've managed to implement that fine.</p> <p>I'd thought I'd try and push myself and try and implement this using a loop and adjusting lower or upper bounds each time.</p> <p>Here is my code:</p> <pre><code>#include "std_lib_facilities.h" int main( ){ int count = 0; int lowerBound = 0; int upperBound = 100; string userInput = ""; while ( lowerBound != upperBound ){ // Increment count ++count; int halfRange = 0; // Make halfRange a while number, round up if any decimal portion. double range = ( upperBound - lowerBound ) / 2; int rangeDelta = range - (int)range; if ( rangeDelta != 0 ) halfRange = (int)range + 1; else halfRange = range; cout &lt;&lt; count &lt;&lt;": Is your number between " &lt;&lt; lowerBound &lt;&lt; " and " &lt;&lt; lowerBound + halfRange &lt;&lt; "? "; cin &gt;&gt; userInput; // Reset the bounds if ( userInput == "y" || userInput == "Y" ) upperBound -= halfRange; else if ( userInput == "n" || userInput == "n" ) lowerBound += halfRange; else { --count; cout &lt;&lt; "Error! Answer could not be understood."; } } cout &lt;&lt; "lowerBound: " &lt;&lt; lowerBound &lt;&lt; ", upperBound: " &lt;&lt; upperBound &lt;&lt; "\n\n"; cout &lt;&lt; "Your number is: " &lt;&lt; lowerBound &lt;&lt; "\n"; return 0; } </code></pre> <p>The problem? Well, it occurs when it gets to numbers where there is a decimal portion and using integer division, which throws the decimal part away. If you use the number 48, the program guesses to 47 and 47.</p> <p>Any clues to get me going? I think I'm quite close, but will appreciate some help.</p> <p>Thanks,</p> <p>Matt</p>
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    1. COIt sounds like it would be better as `int halfRange = std::ceil((upperBound - lowerBound) / 2.0);`. `ceil` takes a floating-point number and returns that rounded up. Alternatively, it looks like `std::rint` with a rounding style of always up would do the trick and return an integral type as well.
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    2. COTo be honest, I would get rid of floating-point math *entirely*.
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    3. CO@NPE, True, it's not nearly as bad to do so here as it could be.
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