recursion - JAVA Recursive Program logic -

recursion - JAVA Recursive Program logic -

public class prod { public static void main(string[] args) { system.out.println(prod(1, 4)); } public static int prod(int m, int n) { if (m == n) { homecoming n; } else { int recurse = prod(m, n-1); int result = n * recurse; homecoming result; } } }

on running above code , 24 ? don't quite understand how?

my doubts: 1. when m =1 , n=4 , phone call prod until m , n become equal 1. output should n , else block should not executed??

someone please help me understand logic.

just run through numbers, need write downwards see behavior (in future, suggest adding lots of prints code check variables , how alter each pass through).

prod(1,4) m=1,n=4 m != n so, recurse = prod(1, 3) prod(1, 3) m=1,n=3 m != n so, recurse = prod(1, 2) prod(1, 2) m=1,n=2 m != n so, recurse = prod(1, 1) prod(1, 1) m=1,n=1 m == n so, homecoming 1 returns prod(1, 2) recurse = 1 result = 2 * 1 homecoming 2 returns prod(1, 3) recurse = 2 result = 3 * 2 homecoming 6 returns prod(1, 4) recurse = 6 result = 4 * 6 homecoming 24

thus, programme prints 24.

sometimes best way figure out programme mechanically go through steps line line, executing them in head (or on paper track things).

java recursion