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comparison 2017/day25.d @ 32:763c88851b91

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day 25
author Jordi Gutiérrez Hermoso <jordigh@octave.org>
date Tue, 02 Jan 2018 21:41:45 -0500
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31:6761b3bbaa70 32:763c88851b91
1 import std.stdio;
2 import std.format: formattedRead;
3 import std.algorithm: sum;
4
5 struct Branch {
6 bool writeval;
7 int movedir;
8 char newstate;
9 }
10
11 struct Instruction {
12 Branch if0;
13 Branch if1;
14 }
15
16 auto branchFmt =
17 " - Write the value %d.
18 - Move one slot to the %s.
19 - Continue with state %s.
20 ";
21
22 auto parseBranch(File f) {
23 int writeval;
24 string movedir;
25 char newstate;
26
27 f.readf(branchFmt, &writeval, &movedir, &newstate);
28 return Branch(writeval ? true : false, movedir == "left" ? -1 : 1, newstate);
29 }
30
31 auto parseInstructions(File f) {
32 Instruction[char] instructions;
33
34 while(!f.eof) {
35 char state;
36 f.readf("In state %s:\n", &state);
37 f.readln; // "If the current value is 0:"
38 auto if0 = f.parseBranch;
39 f.readln; // "If the current value is 1:"
40 auto if1 = f.parseBranch;
41 f.readln; // Blank line
42 instructions[state] = Instruction(if0, if1);
43 }
44 return instructions;
45 }
46
47 auto runProgram(File f) {
48 char state;
49 f.readf("Begin in state %s.\n", &state);
50
51 long steps;
52 f.readf("Perform a diagnostic checksum after %d steps.\n\n", &steps);
53
54 Instruction[char] instructions = f.parseInstructions;
55 long ip = 0;
56 bool[long] tape;
57
58 foreach(_; 0..steps) {
59 auto inst = instructions[state];
60 auto branch = tape.get(ip, false) ? inst.if1 : inst.if0;
61 tape[ip] = branch.writeval;
62 ip += branch.movedir;
63 state = branch.newstate;
64 }
65 return tape.values.sum;
66 }
67
68 void main(string[] args){
69 auto checkSum = runProgram(File(args[1]));
70 writeln(checkSum);
71 }