java - Not able to understand this recursion -

java - Not able to understand this recursion -

the input {4,7,3,6,7} , output is:

[81] [40, 41] [21, 19, 22] [11, 10, 9, 13] [4, 7, 3, 6, 7]

the recursive programme have below, have added print statements understand recursion:

import java.util.arrays; public class triangle_array { public static void print(int a[]) { if(a.length==0) return; int n=a.length; int newa[]=new int[n-1]; for(int i=0;i<n-1;i++) { newa[i]=a[i]+a[i+1]; } system.out.println("here1") ; print(newa); system.out.println("here2") ; if(newa.length!=0) system.out.println(arrays.tostring(newa)); } public static void main(string args[]) { int a[]={4,7,3,6,7}; print(a); system.out.println(arrays.tostring(a)); } }

i got output as:

here1 here1 here1 here1 here1 here2 here2 [81] here2 [40, 41] here2 [21, 19, 22] here2 [11, 10, 9, 13] [4, 7, 3, 6, 7]

i not able understand recursion, above here statements, understand print methos beingness called recursively first, , when status fails, returns outside of print , goes line , prints "here2" 2 times , verifies length of newa zero, until point understood, in next iterations how length of newa increment , how below status become true, println statement ?

in general, if there prints in recursive method, prints come before recursive phone call printed in order of increasing recursion depth, , prints come after recursive phone call printed in reverse order.

public static void demorecursion( int n, int depth ) { if ( n <= 0 ) { return; } system.out.println( "before recursive call, depth " + depth ); demorecursion( n - 1, depth + 1 ); system.out.println( "after recursive call, depth " + depth ); }

if phone call method using demorecursion( 3, 1 ) you'll get:

class="lang-none prettyprint-override">before recursive call, depth 1 before recursive call, depth 2 before recursive call, depth 3 after recursive call, depth 3 after recursive call, depth 2 after recursive call, depth 1

so it's not if a increasing in size. it's @ depth 1, have 5 item array, @ depth 2, have 4 item array, @ depth 3, have 3 , on.

so because of reverse printing effect demonstrated above, each depth`s array printed after array of deeper level, shorter.

if had printed array before recursive call, prints have been in decreasing order.

java recursion