add day 8

1 files changed, 124 insertions, 0 deletions

diff --git a/day_08.zig b/day_08.zig
new file mode 100644
index 0000000..4b5ae38
--- /dev/null
+++ b/day_08.zig
@@ -0,0 +1,124 @@
+const std = @import("std");
+const Result = @import("util/aoc.zig").Result;
+
+pub fn puzzle_1(input: []const u8) Result {
+    var grid = std.mem.zeroes([99][99]u8);
+    load_grid(&grid, input);
+
+    var count: i32 = 0;
+
+    for (grid) |_, y| {
+        for (grid[y]) |_, x| {
+            const position = [_]usize{ y, x };
+            if (is_visible_left(position, grid) or
+                is_visible_right(position, grid) or is_visible_up(position, grid) or
+                is_visible_down(position, grid)) count += 1;
+        }
+    }
+
+    return .{ .int = count };
+}
+
+pub fn puzzle_2(input: []const u8) Result {
+    var grid = std.mem.zeroes([99][99]u8);
+    load_grid(&grid, input);
+
+    var max: u32 = 0;
+
+    for (grid) |_, y| {
+        for (grid[y]) |_, x| {
+            const position = [_]usize{ y, x };
+            const down = view_distance_down(position, grid);
+            const left = view_distance_left(position, grid);
+            const right = view_distance_right(position, grid);
+            const up = view_distance_up(position, grid);
+
+            const n: u32 = down * up * left * right;
+            max = std.math.max(n, max);
+        }
+    }
+
+    return .{ .int = @intCast(i32, max) };
+}
+
+fn load_grid(grid: *[99][99]u8, input: []const u8) void {
+    var iter = std.mem.split(u8, input, "\n");
+    var row_idx: usize = 0;
+    while (iter.next()) |line| : (row_idx += 1) {
+        for (line) |char, column| {
+            grid[row_idx][column] = std.fmt.parseInt(u8, &[_]u8{char}, 0) catch unreachable;
+        }
+    }
+}
+
+fn is_visible_down(pos: [2]usize, grid: [99][99]u8) bool {
+    var max = grid[pos[0]][pos[1]];
+    var i = pos[0] + 1;
+    for (grid[i..]) |_| {
+        if (grid[i][pos[1]] >= max) return false;
+        i += 1;
+    }
+    return true;
+}
+
+fn is_visible_up(pos: [2]usize, grid: [99][99]u8) bool {
+    var max = grid[pos[0]][pos[1]];
+    for (grid[0..pos[0]]) |row| if (row[pos[1]] >= max) return false;
+    return true;
+}
+
+fn is_visible_right(pos: [2]usize, grid: [99][99]u8) bool {
+    var max = grid[pos[0]][pos[1]];
+    for (grid[pos[0]][pos[1] + 1 ..]) |n| if (n >= max) return false;
+    return true;
+}
+
+fn is_visible_left(pos: [2]usize, grid: [99][99]u8) bool {
+    var max = grid[pos[0]][pos[1]];
+    for (grid[pos[0]][0..pos[1]]) |n| if (n >= max) return false;
+    return true;
+}
+
+fn view_distance_down(pos: [2]usize, grid: [99][99]u8) u32 {
+    var max = grid[pos[0]][pos[1]];
+    var treecount: u8 = 0;
+    var i = pos[0] + 1;
+    for (grid[i..]) |_| {
+        if (grid[i][pos[1]] >= max) return treecount + 1;
+        treecount += 1;
+        i += 1;
+    }
+    return treecount;
+}
+
+fn view_distance_right(pos: [2]usize, grid: [99][99]u8) u32 {
+    var max = grid[pos[0]][pos[1]];
+    var treecount: u8 = 0;
+    for (grid[pos[0]][pos[1] + 1 ..]) |n| {
+        if (n >= max) return treecount + 1;
+        treecount += 1;
+    }
+    return treecount;
+}
+
+fn view_distance_up(pos: [2]usize, grid: [99][99]u8) u32 {
+    var max = grid[pos[0]][pos[1]];
+    var treecount: u8 = 0;
+    var i: usize = pos[0];
+    while (i > 0) : (treecount += 1) {
+        i -= 1;
+        if (grid[i][pos[1]] >= max) return treecount + 1;
+    }
+    return treecount;
+}
+
+fn view_distance_left(pos: [2]usize, grid: [99][99]u8) u32 {
+    var max = grid[pos[0]][pos[1]];
+    var treecount: u8 = 0;
+    var i: usize = pos[1];
+    while (i > 0) : (treecount += 1) {
+        i -= 1;
+        if (grid[pos[0]][i] >= max) return treecount + 1;
+    }
+    return treecount;
+}