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# Recursion - PowerPoint PPT Presentation

Recursion. Brian Toone 10/14/09. Recursion. When a method calls itself Example int factorial(n) { if (n<=1) return 1; else return n*factorial(n-1); }. Properties of recursion. All recursion must end Base case The condition which terminates the recursion

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### Recursion

Brian Toone

10/14/09

• When a method calls itself

• Example

int factorial(n) {

if (n<=1)

return 1;

else

return n*factorial(n-1);

}

• All recursion must end

• Base case

• The condition which terminates the recursion

• Each recursive call should make progress towards base case

• Factorial – the base case occurs when n <= 1

int factorial(n) {

if (n<=1)

return 1;

else

return n*factorial(n-1);

}

• Display all possible orderings of the letters in the word “carbon”

• Recursive solution

• Concatenate ‘c’ to the beginning of each ordering returned from a recursive call made on “arbon”

• Concatenate ‘a’ to the beginning of each ordering returned from a recursive call made on “crbon”

• The recursive call is made to obtain the orderings of the subwords “arbon”, “crbon”, “cabon”, “caron”

• Base case: only one letter - simply return it