Advent of Code Day 18 recursion for flood fill

[iglesias]

1 deltas = {{+1,0,0}, {0,+1,0}, {0,0,+1}};
1 for(int x{0}; x<N; x++)
2 for(int y{0}; y<N; y++)
3 flood(x,y,0);
4
5 for(int y{0}; y<N; y++)
6 for(int z{0}; z<N; z++)
7 flood(0,y,z);
8
9 for(int x{0}; x<N; x++)
10 for(int z{0}; z<N; z++)
11 flood(x,0,z);
12
13
14
15 for(int x{0}; x<N; x++)
16 for(int y{0}; y<N; y++)
17 {
18 flood(x,y,0, ::p(0,0,+1));
19 flood(x,y,N-1,::p(0,0,-1));
20
21 flood(x,y,0, ::p(+1,0,0));
22 flood(x,y,0, ::p(0,+1,0));
23 }
24
25 for(int y{0}; y<N; y++)
26 for(int z{0}; z<N; z++)
27 {
28 flood(0,y,z, ::p(+1,0,0));
29 flood(N-1,y,z,::p(-1,0,0));
30
31 flood(0,y,z, ::p(0,+1,0));
32 flood(0,y,z, ::p(0,0,+1));
33 }
34
35 for(int x{0}; x<N; x++)
36 for(int z{0}; z<N; z++)
37 {
38 flood(x,0,z, ::p(0,+1,0));
39 flood(x,N-1,z,::p(0,-1,0));
40
41 flood(x,0,z, ::p(+1,0,0));
42 flood(x,0,z, ::p(0,0,+1));
43 }

[iglesias]

Compare the first recursion to the second one.