feat: solve puzzle 3

03/SCRATCH.md

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+# Notes
+
+## Contraints
+
+- Periods don't count as special characters
+- All lines have same length
+- If not a number or period then it is a special character
+
+Each line parsed need to collect all numbers.
+
+Can't know whether a collected number is a part number until we
+have also parsed the proceeding or following line.
+
+```text
+467..114..
+...*......
+..35..633.
+......#...
+617*......
+```
+
+After parsing first line we would have `467` with start index 0 and end index 2 and `114` with start index 5 and end index 7.
+
+For 467 to be a part number it needs to have a special character at index 3 or it needs to have a special character at index 1, 2, 3, 4 on the next line.
+
+For 114 to be a part number it needs to have a special character at index 4 or index 8 or it needs to have a special character at index 4, 5, 6, 7 on the next line.
+
+Need to keep track of:
+
+- Previous line - will start as empty
+- Current line
+- Next line
+
+So you look at the current line and you parse all the numbers with their start and end index. You also parse all special characters with their index.
+
+Then you end up with something like this: currentLine
+
+```json
+{
+  "numbers": [
+    "467": {
+      "start": 0,
+      "end": 2
+    },
+    "114": {
+      "start": 5,
+      "end": 7
+    }
+  ],
+  "specialCharacters": []
+}
+```
+
+```csharp
+var currentLineString = "467..114..";
+var currentLine = new Line(currentLineString);
+
+class Line
+{
+  public List<Dictionary<int, Indexes>> Numbers { get; set; }
+  public List<Dictionary<int, Indexes>> SpecialCharacters { get; set; }
+
+  public Line(string line)
+  {
+    // parse line
+  }
+}
+
+public class Indexes
+{
+  public int Start { get; set; }
+  public int End { get; set; }
+
+  public Indexes(int start, int length)
+  {
+    Start = start;
+    End = start + length;
+  }
+}
+```
+
+Then you see if those numbers are part numbers just by checking if a special character proceeds or follows their start and end indexes.
+
+```csharp
+```
+
+If not then you need to see if there is a previous line and whether there is a special character at on the previous line that has an index that is between 1 less than the start index and 1 more than the end index.
+
+If not then you need to see if there is a next line and whether there is a special character at on the next line that has an index that is between 1 less than the start index and 1 more than the end index.
+```