demo-combinations - } int Factorial(int x) // PRE: x...

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// Programmer: Doug Hogan // Section: N/A // Program: Demo: Factorial, Permutations, Combinations // Date: October 12, 2008 // Description: This program computes the factorial using a function and demonstrates // a function using another function (and will be used for class // discussion on prototypes). // ????????????????????????????????????????????????????????????????????? // CLASS DISCUSSION QUESTION: WILL THIS ONE WORK? WHY OR WHY NOT? // ????????????????????????????????????????????????????????????????????? #include <iostream> using namespace std; int NumPermutations(int n, int r) // PRE: // POST: FCTVAL == number of ways to arrange r objects chosen from n { return Factorial(n)/Factorial(n-r);
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Unformatted text preview: } int Factorial(int x) // PRE: x &gt;= 0 // POST: FCTVAL == x!, i.e. the factorial of x { int result = 1; // factorial of x; starts at 1 // as we'll multiply by it and // as 0! = 1 for(int i = 1; i &lt;= x; i++) // multiply result by all numbers { // b/w 1 and x to find factorial result = result * i; } return result; } int NumCombinations(int n, int r) // PRE: n &gt; 0 &amp;&amp; r &gt;= 0 &amp;&amp; r &lt;= n // POST: FCTVAL == number of ways to choose r objects chosen from n // (without regard to order) { return NumPermutations(n, r)/Factorial(r); } int main() { cout &lt;&lt; &quot;P(5, 2) = &quot; &lt;&lt; NumPermutations(5, 2) &lt;&lt; endl; cout &lt;&lt; &quot;5 choose 2 = &quot; &lt;&lt; NumCombinations(5, 2) &lt;&lt; endl; return 0; }...
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