The first lecture of DSA was already interesting for me, I learned something about “Mutual Recursion” (when two procedures call each other). The pseudo-code example was about checking if a number is either even or odd.
Given that
- 0 is even
- N is even if n-1 is odd
- N is odd if n-1 is even
And the algorithm:
even INPUT: n – a natural number. OUTPUT: true if n is even; false otherwise odd(n) if n = 0 then return FALSE return even(n-1) even(n) if n = 0 then return TRUE else return odd(n-1)
I implemented a tiny C program which uses it:
#include <stdio.h> int main (int argc, char const *argv[]) { // set an integer number here int number = 23945; // if the number is odd (1 = TRUE) if(odd(number)==1) printf("%d is odd\n",number); else printf("%d is even\n",number); return 0; } // returns 0 if the given number becomes 0, so the given number is odd // returns even(number - 1) elsewhere int odd(int number){ if (number==0) return 0; else return even(number-1); } // returns 0 if the given number becomes 0, so the given number is even // returns odd(number - 1) elsewhere int even(int number){ if(number==0) return 1; else return odd(number-1); } |
Let’s see if I can keep understanding things at DSA 
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