day 4 part 2

diff --git a/day4/src/main.zig b/day4/src/main.zig
index 4f736ff9b210670856331ae4fb4e2acb70547a7c..e3c83f58f486e7af4640ad403831294947920455 100644 (file)
--- a/day4/src/main.zig
+++ b/day4/src/main.zig
@@ -1,9 +1,84 @@
 const std = @import("std");
 const day4 = @import("day4");
 
-// test "is invalid" {
-//     try std.testing.expect(isInvalid("11", 1) == true);
-// }
+test "idx test" {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    defer _ = gpa.deinit();
+    const alloc = gpa.allocator();
+
+    // Read contents from file "./filename"
+    const cwd = std.fs.cwd();
+    const fileContents = try cwd.readFileAlloc(alloc, "day4_test.txt", 24000);
+    defer alloc.free(fileContents);
+
+    // Print file contents
+    // std.debug.print("{s}", .{fileContents});
+    var lines = std.mem.splitScalar(u8, fileContents, '\n');
+
+    const line = lines.peek() orelse unreachable;
+    const col_count = line.len;
+
+    var grid = std.array_list.Aligned(bool, null).empty;
+    defer grid.deinit(alloc);
+
+    // put in all @
+    var r: u64 = 0;
+    while (lines.next()) |row| : (r += 1) {
+        if (row.len == 0) {
+            break;
+        }
+        std.debug.print("row: {s}\n", .{row});
+        for (row) |v| {
+            if (v == '@') {
+                try grid.append(alloc, true);
+            } else {
+                try grid.append(alloc, false);
+            }
+        }
+    }
+
+    // const row_count = r / col_count;
+    try std.testing.expect(grid.items[idx(0, 0, col_count)] == false);
+    try std.testing.expect(grid.items[idx(0, 1, col_count)] == false);
+    try std.testing.expect(grid.items[idx(0, 2, col_count)] == true);
+    try std.testing.expect(grid.items[idx(0, 3, col_count)] == true);
+    try std.testing.expect(grid.items[idx(0, 4, col_count)] == false);
+    try std.testing.expect(grid.items[idx(0, 5, col_count)] == true);
+    try std.testing.expect(grid.items[idx(0, 6, col_count)] == true);
+    try std.testing.expect(grid.items[idx(0, 7, col_count)] == true);
+    try std.testing.expect(grid.items[idx(0, 8, col_count)] == true);
+    try std.testing.expect(grid.items[idx(0, 9, col_count)] == false);
+
+    try std.testing.expect(grid.items[idx(1, 0, col_count)] == true);
+    try std.testing.expect(grid.items[idx(1, 1, col_count)] == true);
+    try std.testing.expect(grid.items[idx(1, 2, col_count)] == true);
+    try std.testing.expect(grid.items[idx(1, 3, col_count)] == false);
+    try std.testing.expect(grid.items[idx(1, 4, col_count)] == true);
+    try std.testing.expect(grid.items[idx(1, 5, col_count)] == false);
+    try std.testing.expect(grid.items[idx(1, 6, col_count)] == true);
+    try std.testing.expect(grid.items[idx(1, 7, col_count)] == false);
+    try std.testing.expect(grid.items[idx(1, 8, col_count)] == true);
+    try std.testing.expect(grid.items[idx(1, 9, col_count)] == true);
+}
+
+const Position = struct {
+    row: u64,
+    col: u64,
+};
+
+fn idx(r: usize, c: usize, col_count: usize) usize {
+    return r * col_count + c;
+}
+
+const MAX_POTENTIAL_CHANGES = 8;
+const AppendError = error{Full};
+fn append(arr: *[MAX_POTENTIAL_CHANGES]Position, arr_len: *usize, val: Position) (AppendError!void) {
+    if (arr_len.* >= arr.*.len) {
+        return error.Full;
+    }
+    arr[arr_len.*] = val;
+    arr_len.* += 1;
+}
 
 pub fn main() !void {
     // Initiate allocator
@@ -18,94 +93,142 @@ pub fn main() !void {
 
     // Print file contents
     // std.debug.print("{s}", .{fileContents});
-    var splits = std.mem.splitScalar(u8, fileContents, '\n');
+    var lines = std.mem.splitScalar(u8, fileContents, '\n');
+
+    const line = lines.peek() orelse unreachable;
+    const col_count = line.len;
 
     var accessible_rolls: u64 = 0;
-    const line = splits.peek() orelse return;
-    const len: usize = line.len;
-    std.debug.assert(len > 0);
-    var prev = try std.array_list.Aligned(u8, null).initCapacity(alloc, len);
-    var next = try std.array_list.Aligned(u8, null).initCapacity(alloc, len);
-    defer prev.deinit(alloc);
-    defer next.deinit(alloc);
-
-    try prev.resize(alloc, len);
-    try next.resize(alloc, len);
-
-    @memset(prev.items, '.');
-    @memset(next.items, '.');
-    // std.debug.print("prev items{s}\n\n", .{prev.items});
-    // std.debug.print("next items{s}\n\n", .{next.items});
-    var ind: u64 = 0;
-    while (splits.next()) |row| {
-        // std.debug.print("split: {s}\n", .{row});
-        if (row.len < 1) {
-            ind += 1;
-            continue;
-        }
-        if (splits.peek()) |next_line| {
-            // std.debug.print("next_line len={} hex={s}\n", .{ next_line.len, next_line });
+    var changes = std.array_list.Aligned(Position, null).empty;
+    defer changes.deinit(alloc);
 
-            if (next_line.len > 0) {
-                @memcpy(next.items[0..next_line.len], next_line);
+    var grid = std.array_list.Aligned(bool, null).empty;
+    defer grid.deinit(alloc);
+
+    var next_grid = std.array_list.Aligned(bool, null).empty;
+    defer next_grid.deinit(alloc);
+
+    // put in all @
+    var r: u64 = 0;
+    while (lines.next()) |row| : (r += 1) {
+        if (row.len == 0) {
+            break;
+        }
+        std.debug.print("row: {s}\n", .{row});
+        for (row, 0..) |v, c| {
+            if (v == '@') {
+                try changes.append(alloc, Position{ .row = r, .col = c });
+                try grid.append(alloc, true);
             } else {
-                @memset(next.items, '.');
+                try grid.append(alloc, false);
             }
-        } else {
-            @memset(next.items, '.');
         }
+    }
+
+    const row_count = r;
 
-        std.debug.print("prev: {s}\nrow:  {s}\nnext: {s}\n", .{ prev.items, row, next.items });
-        for (0..len) |i| {
-            if (row[i] != '@') {
+    try next_grid.resize(alloc, grid.items.len);
+    @memcpy(next_grid.items, grid.items);
+
+    var current_head: usize = 0;
+    var changes_made = true;
+    std.debug.print("COL_COUNT:{}, ROW_COUNT:{}\n\n\n", .{ col_count, row_count });
+
+    var seen = std.hash_map.AutoHashMap(Position, bool).init(alloc);
+    defer seen.deinit();
+
+    while (changes_made) {
+        for (grid.items, 0..) |value, j| {
+            if (j % col_count == 0 and j != 0) {
+                std.debug.print("\n", .{});
+            }
+            if (value) {
+                std.debug.print("@", .{});
+            } else {
+                std.debug.print(".", .{});
+            }
+        }
+        std.debug.print("\n", .{});
+        const current_changes_len = changes.items.len;
+        for (current_head..current_changes_len) |i| {
+            const pos = changes.items[i];
+            if (seen.get(pos) orelse false) {
                 continue;
             }
-            var surround: u64 = 0;
-            if (i > 0) { // left
-                if (prev.items[i - 1] == '@') {
-                    surround += 1;
-                    std.debug.print("i={}, src=prev_left, surround now={}\n", .{ i, surround });
+            var potential_changes: [MAX_POTENTIAL_CHANGES]Position = undefined;
+            var potential_changes_len: usize = 0;
+            std.debug.print("index: i{}, current head{} current_changes_len{} | ", .{ i, current_head, current_changes_len });
+            std.debug.print("Position: [{}, {}] idx{} | ", .{ pos.row, pos.col, idx(pos.row, pos.col, col_count) });
+            // if (!grid.items[idx(pos.row, pos.col, col_count)]) {
+            //     continue;
+            // }
+            var surrounding: u64 = 0;
+            if (pos.row > 0) {
+                if (pos.col > 0) {
+                    if (grid.items[idx(pos.row - 1, pos.col - 1, col_count)]) {
+                        surrounding += 1;
+                        try append(&potential_changes, &potential_changes_len, Position{ .row = pos.row - 1, .col = pos.col - 1 });
+                    }
                 }
-                if (row[i - 1] == '@') {
-                    surround += 1;
-                    std.debug.print("i={}, src=row_left, surround now={}\n", .{ i, surround });
+                if (grid.items[idx(pos.row - 1, pos.col, col_count)]) {
+                    surrounding += 1;
+                    try append(&potential_changes, &potential_changes_len, Position{ .row = pos.row - 1, .col = pos.col });
                 }
-                if (next.items[i - 1] == '@') {
-                    surround += 1;
-                    std.debug.print("i={}, src=next_left, surround now={}\n", .{ i, surround });
+                if (pos.col + 1 < col_count) {
+                    if (grid.items[idx(pos.row - 1, pos.col + 1, col_count)]) {
+                        surrounding += 1;
+                        try append(&potential_changes, &potential_changes_len, Position{ .row = pos.row - 1, .col = pos.col + 1 });
+                    }
                 }
             }
-            if (prev.items[i] == '@') {
-                surround += 1;
-                std.debug.print("i={}, src=prev_mid, surround now={}\n", .{ i, surround });
+            if (pos.col > 0) {
+                if (grid.items[idx(pos.row, pos.col - 1, col_count)]) {
+                    surrounding += 1;
+                    try append(&potential_changes, &potential_changes_len, Position{ .row = pos.row, .col = pos.col - 1 });
+                }
             }
-            if (next.items[i] == '@') {
-                surround += 1;
-                std.debug.print("i={}, src=next_mid, surround now={}\n", .{ i, surround });
+            if (pos.col + 1 < col_count) {
+                if (grid.items[idx(pos.row, pos.col + 1, col_count)]) {
+                    surrounding += 1;
+                    try append(&potential_changes, &potential_changes_len, Position{ .row = pos.row, .col = pos.col + 1 });
+                }
             }
-            if (i < row.len - 1) { // right
-                if (prev.items[i + 1] == '@') {
-                    surround += 1;
-                    std.debug.print("i={}, src=prev_right, surround now={}\n", .{ i, surround });
+            if (pos.row + 1 < row_count) {
+                if (pos.col > 0) {
+                    if (grid.items[idx(pos.row + 1, pos.col - 1, col_count)]) {
+                        surrounding += 1;
+                        try append(&potential_changes, &potential_changes_len, Position{ .row = pos.row + 1, .col = pos.col - 1 });
+                    }
                 }
-                if (row[i + 1] == '@') {
-                    surround += 1;
-                    std.debug.print("i={}, src=row_right, surround now={}\n", .{ i, surround });
+                if (grid.items[idx(pos.row + 1, pos.col, col_count)]) {
+                    surrounding += 1;
+                    try append(&potential_changes, &potential_changes_len, Position{ .row = pos.row + 1, .col = pos.col });
                 }
-                if (next.items[i + 1] == '@') {
-                    surround += 1;
-                    std.debug.print("i={}, src=next_right, surround now={}\n", .{ i, surround });
+                if (pos.col + 1 < col_count) {
+                    if (grid.items[idx(pos.row + 1, pos.col + 1, col_count)]) {
+                        surrounding += 1;
+                        try append(&potential_changes, &potential_changes_len, Position{ .row = pos.row + 1, .col = pos.col + 1 });
+                    }
                 }
             }
-            std.debug.print("surround: {}, ", .{surround});
-            if (surround < 4) {
+            if (surrounding < 4) {
                 accessible_rolls += 1;
+                next_grid.items[idx(pos.row, pos.col, col_count)] = false;
+                std.debug.print("(r:{}, c:{}) surrounding: {}", .{ pos.row, pos.col, surrounding });
+                const potential_changes_slice = potential_changes[0..potential_changes_len];
+                try changes.appendSlice(alloc, potential_changes_slice);
+                try seen.put(pos, true);
             }
-            ind += 1;
+            std.debug.print("\n", .{});
+        }
+
+        std.debug.print("\n rolls: {}\n\n", .{accessible_rolls});
+        if (changes.items.len == current_changes_len) {
+            changes_made = false;
         }
-        std.debug.assert(prev.items.len == row.len);
-        @memcpy(prev.items, row);
-        std.debug.print("rolls running total {}\n\n", .{accessible_rolls});
+        current_head = current_changes_len;
+        @memcpy(grid.items, next_grid.items);
+        // return;
     }
 
     std.debug.print("accessible rolls: {}\n", .{accessible_rolls});