advent-of-code

commit 7f14e603d8cb16776ae5c789bf1fad9b9c328ac9
parent 8d4848d3260121fadcdeda4ae90c8a330f65634f
Author: amin <dev@aminmesbah.com>
Date:   Sat,  1 Dec 2018 19:59:31 +0000

Add solution for 01-2

FossilOrigin-Name: 60927fe14d9add066d04bb3afa77d78232a4dae7b63524cff23de83220005b4d
Diffstat:
M
main.zig
 | 
49
++++++++++++++++++++++++++++++++++++++++++++++---

1 file changed, 46 insertions(+), 3 deletions(-)
diff --git a/main.zig b/main.zig
@@ -7,10 +7,11 @@ const os = std.os;
 
 pub fn main() !void {
     var allocator = &std.heap.DirectAllocator.init().allocator;
-    var input = try get_file_contents(allocator, "input_01.txt");
-    defer allocator.free(input);
+    var input01 = try get_file_contents(allocator, "input_01.txt");
+    defer allocator.free(input01);
 
-    debug.warn("01-1: {}\n", total_sum(input));
+    debug.warn("01-1: {}\n", total_sum(input01));
+    debug.warn("01-2: {}\n", first_visited_twice(input01));
 }
 
 fn total_sum(input: []const u8) !i32 {
@@ -35,6 +36,48 @@ test "total_sum" {
     debug.assert(41 == try total_sum(s));
 }
 
+fn first_visited_twice(input: []const u8) !i32 {
+    var sum: i32 = 0;
+    var index: usize = 0;
+
+    const visited_magnitude: usize = 1000000;
+    const visited_size: usize = (visited_magnitude * 2) + 1;
+    // [ -visited_magnitude, ..., -3, -2, -1, 0, 1, 2, 3, ..., visited_magnitude ]
+    var visited = []bool{false} ** visited_size;
+
+    //debug.warn("{} ", sum);
+    while (true) {
+        var visited_index = @intCast(usize, @intCast(i32, visited_magnitude) + sum);
+        debug.assert(visited_index >= 0);
+        if (visited[visited_index] == true) {
+            return sum;
+        } else {
+            visited[visited_index] = true;
+        }
+
+        var e = index;
+        while (input[e] != '\n') {
+            e += 1;
+        }
+        debug.assert('\n' == input[e]);
+
+        var num = try fmt.parseInt(i32, input[index..e], 10);
+        sum += num;
+        //debug.warn("+ {}\n", num);
+        //debug.warn("{} ", sum);
+        index = (e + 1) % input.len;
+    }
+    debug.warn("\n---\n");
+    return sum;
+}
+
+test "first_visited_twice" {
+    debug.assert(0 == try first_visited_twice("+1\n-1\n"));
+    debug.assert(10 == try first_visited_twice("+3\n+3\n+4\n-2\n-4\n"));
+    debug.assert(5 == try first_visited_twice("-6\n+3\n+8\n+5\n-6\n"));
+    debug.assert(14 == try first_visited_twice("+7\n+7\n-2\n-7\n-4\n"));
+}
+
 fn get_file_contents(allocator: *mem.Allocator, file_name: []const u8) ![]u8 {
     var file = try os.File.openRead(file_name);
     defer file.close();