diff --git a/inputs/day10.example.txt b/inputs/day10.example.txt
new file mode 100644
index 0000000..cada9b3
--- /dev/null
+++ b/inputs/day10.example.txt
@@ -0,0 +1,8 @@
+89010123
+78121874
+87430965
+96549874
+45678903
+32019012
+01329801
+10456732
diff --git a/inputs/day10.txt b/inputs/day10.txt
new file mode 100644
index 0000000..7221523
--- /dev/null
+++ b/inputs/day10.txt
@@ -0,0 +1,59 @@
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diff --git a/src/day10-2.zig b/src/day10-2.zig
new file mode 100644
index 0000000..6032401
--- /dev/null
+++ b/src/day10-2.zig
@@ -0,0 +1,81 @@
+const std = @import("std");
+const print = std.debug.print;
+const args = @import("lib/args.zig");
+const files = @import("lib/files.zig");
+
+inline fn normalize(c: u8) u8 {
+    return switch (c) {
+        '0'...'9' => c - '0',
+        else => unreachable,
+    };
+}
+
+fn printMap(m: [60][60]u8, size: usize) void {
+    for (0..size) |y| {
+        for (0..size) |x| {
+            print("{c}", .{m[y][x]});
+        }
+        print("\n", .{});
+    }
+}
+
+// This approach does not take into account trails tha bifurcate.
+//
+// By the problem definition:
+//
+//   0
+//   1
+// 43234
+// 5   5
+// 6   6
+// 78987
+//
+// The example above contains one trilhead with a score of one, but this
+// implementation would considerit a a score of 2.
+fn updateScores(m: [60][60]u8, s: *[60][60]u16, size: usize, y: usize, x: usize) void {
+    if (m[y][x] == '0') {
+        s[y][x] += 1;
+        return;
+    }
+    const c = m[y][x];
+    if (x > 0 and m[y][x - 1] == c - 1) {
+        updateScores(m, s, size, y, x - 1);
+    }
+    if (x < size - 1 and m[y][x + 1] == c - 1) {
+        updateScores(m, s, size, y, x + 1);
+    }
+    if (y > 0 and m[y - 1][x] == c - 1) {
+        updateScores(m, s, size, y - 1, x);
+    }
+    if (y < size - 1 and m[y + 1][x] == c - 1) {
+        updateScores(m, s, size, y + 1, x);
+    }
+}
+
+pub fn main() !void {
+    const input_path = args.getFirstArg();
+    const input = try files.openForReading(input_path);
+
+    var map: [60][60]u8 = undefined;
+    var scores: [60][60]u16 = .{.{0} ** 60} ** 60;
+    var map_size: usize = 0;
+    while (files.readLine(input, &map[map_size])) |_| : (map_size += 1) {} else |err| {
+        print("done reading input with error: {any}\n", .{err});
+    }
+
+    for (0..map_size) |y| {
+        for (0..map_size) |x| {
+            if (map[y][x] == '9') {
+                updateScores(map, &scores, map_size, y, x);
+            }
+        }
+    }
+
+    var score: usize = 0;
+    for (0..map_size) |y| {
+        for (0..map_size) |x| {
+            score += scores[y][x];
+        }
+    }
+    print("Scores: {d}\n", .{score});
+}
diff --git a/src/day10.zig b/src/day10.zig
new file mode 100644
index 0000000..5c012dd
--- /dev/null
+++ b/src/day10.zig
@@ -0,0 +1,87 @@
+const std = @import("std");
+const print = std.debug.print;
+const args = @import("lib/args.zig");
+const files = @import("lib/files.zig");
+
+inline fn normalize(c: u8) u8 {
+    return switch (c) {
+        '0'...'9' => c - '0',
+        else => unreachable,
+    };
+}
+
+fn printMap(m: [60][60]u8, size: usize) void {
+    for (0..size) |y| {
+        for (0..size) |x| {
+            print("{c}", .{m[y][x]});
+        }
+        print("\n", .{});
+    }
+}
+
+// This approach does not take into account trails tha bifurcate.
+//
+// By the problem definition:
+//
+//   0
+//   1
+// 43234
+// 5   5
+// 6   6
+// 78987
+//
+// The example above contains one trilhead with a score of one, but this
+// implementation would considerit a a score of 2.
+fn updateScores(m: [60][60]u8, s: *[60][60]u16, v: *[60][60]bool, size: usize, y: usize, x: usize) void {
+    if (m[y][x] == '0') {
+        if (!v[y][x]) {
+            s[y][x] += 1;
+            v[y][x] = true;
+        }
+        return;
+    }
+    const c = m[y][x];
+    if (x > 0 and m[y][x - 1] == c - 1) {
+        updateScores(m, s, v, size, y, x - 1);
+    }
+    if (x < size - 1 and m[y][x + 1] == c - 1) {
+        updateScores(m, s, v, size, y, x + 1);
+    }
+    if (y > 0 and m[y - 1][x] == c - 1) {
+        updateScores(m, s, v, size, y - 1, x);
+    }
+    if (y < size - 1 and m[y + 1][x] == c - 1) {
+        updateScores(m, s, v, size, y + 1, x);
+    }
+}
+
+pub fn main() !void {
+    const input_path = args.getFirstArg();
+    const input = try files.openForReading(input_path);
+
+    var map: [60][60]u8 = undefined;
+    var scores: [60][60]u16 = .{.{0} ** 60} ** 60;
+    var visited: [60][60]bool = undefined;
+    var map_size: usize = 0;
+    while (files.readLine(input, &map[map_size])) |_| : (map_size += 1) {} else |err| {
+        print("done reading input with error: {any}\n", .{err});
+    }
+
+    for (0..map_size) |y| {
+        for (0..map_size) |x| {
+            if (map[y][x] == '9') {
+                // We only want to visit every 0 once per 9.
+                @memset(&visited, .{false} ** 60);
+                updateScores(map, &scores, &visited, map_size, y, x);
+            }
+        }
+    }
+
+    var score: usize = 0;
+    for (0..map_size) |y| {
+        for (0..map_size) |x| {
+            score += scores[y][x];
+        }
+    }
+    print("Scores: {d}\n", .{score});
+}