Submitted version of my entry to the N-Queens speed-challenge as part of the lab class Fundamentals of Programming of my first semester at the Technical University of Munich.
Since this was the winning submission (in the category "non-threaded"), I added a progress branch where you can relive my progress from the trivial algorithm to the optimized (fast) algoritm.
You can browse the changes here: progress
Many, many spelling errors :)
I heavily optimized the code so it generates almost optimal byte code for the the chosen algorithmic approach. Here is the byte code generated from the performance-critical function:
private static int findPos(int, int, int, int);
Code:
0: iconst_0
1: istore 4
3: iload_0
4: iload_1
5: iload_2
6: ior
7: iload_3
8: ior
9: iconst_m1
10: ixor
11: iand
12: istore 7
14: iload 7
16: ifle 78
19: iload 7
21: ineg
22: iload 7
24: iand
25: istore 5
27: iload_1
28: iload 5
30: ior
31: istore 6
33: iload 7
35: iload 5
37: ixor
38: istore 7
40: iload 6
42: iload_0
43: if_icmpge 72
46: iload 4
48: iload_0
49: iload 6
51: iload_2
52: iload 5
54: ior
55: iconst_1
56: iushr
57: iload_3
58: iload 5
60: ior
61: iconst_1
62: ishl
63: invokestatic #31 // Method findPos:(IIII)I
66: iadd
67: istore 4
69: goto 14
72: iinc 4, 1
75: goto 14
78: iload 4
80: ireturn