9-2

2024/09/9-2.py

@@ -1,45 +1,113 @@
-import re;
+import re
+
+currentValue = 0
+fileArray = []
+total = 0
+numbersInserted = {}
+
+def printFileStorage():
+    print("".join(fileArray).replace("-", ""))
+
+
+def concatNeighbouringPeriodBlocks():
+    global fileArray
+    index = 0
+    while True:
+        if index+1 == len(fileArray):
+            return
+
+        leftBlock = fileArray[index]
+        rightBlock = fileArray[index+1]
+
+        if "." in leftBlock:
+            if "." in rightBlock:
+                fileArray[index] += fileArray[index+1]
+                del fileArray[index+1]
+            else:
+                index += 1
+        else:
+            index += 1
 
-currentValue = 0;
-fileArray = [];
-total = 0;
 
 def createBlockArray(line):
     global currentValue
     for i, char in enumerate(line):
-        freeSpace = i % 2 == 1;
+        freeSpace = i % 2 == 1
 
         if freeSpace:
-            for _ in range(int(char)):
-                fileArray.append(".")
+            if int(char) != 0:
+                fileArray.append("." * int(char))
         else:
-            for _ in range(int(char)):
-                fileArray.append(currentValue)
+            # It'll be difficult to know whether a block is 9, 99 or 9999, for example
+            # Adding a hyphen after every number will let us use it as a delimiter later
+            fileArray.append((str(currentValue) + "-") * int(char))
+            numbersInserted[currentValue] = int(char)
             currentValue += 1
 
-def sortfileString():
-    global fileString;
-    while True:
-        firstDotIndex = next((idx, space) for idx, space in enumerate(fileArray) if str(space) == ".")[0]
-        lastCharIndex = next((idx, space) for idx, space in enumerate(fileArray[::-1]) if str(space) != ".")[0]
-        lastCharIndex = len(fileArray) - lastCharIndex - 1
-        if firstDotIndex > lastCharIndex:
+def sortFileArray():
+    global fileArray
+    lastUsedIndex = -1
+    uniqueDigits = currentValue - 1
+
+    for digit in range(uniqueDigits, -1, -1):
+        # Starting at the end, find numeric block locations
+        # Find the first available spot for it 
+        # If no spot, move on - only try to move things once
+        for i, blockToMove in enumerate(reversed(fileArray)):
+            if "." in blockToMove:
+                continue
+
+            blockDigit = int(blockToMove.split("-")[0])
+            if digit != blockDigit:
+                continue
+
+            blockTrueSize = numbersInserted[digit]
+            lastUsedIndex = i
             break
-        fileArray[firstDotIndex] = fileArray[lastCharIndex]
-        fileArray[lastCharIndex] = "."
+
+        blockToMoveIndex = len(fileArray) - lastUsedIndex
+        for j in range(blockToMoveIndex):
+            emptySpaceBlock = fileArray[j]
+            if "." not in emptySpaceBlock:
+                continue
+
+            spaceAvailable = len(emptySpaceBlock)
+            if blockTrueSize == spaceAvailable:
+                # overwrite then delete the original block to shrink the list
+                fileArray[j] = blockToMove
+                fileArray[blockToMoveIndex - 1] = "." * spaceAvailable
+                break
+            elif blockTrueSize < spaceAvailable:
+                # gotta make sure we respect the remaining empty space
+                spaceRemaining = spaceAvailable - blockTrueSize
+                spaceUsed = spaceAvailable - spaceRemaining
+                fileArray[blockToMoveIndex - 1] = "." * spaceUsed
+                fileArray[j] = "." * spaceRemaining
+                fileArray.insert(j, blockToMove)
+                break
+        concatNeighbouringPeriodBlocks()
 
 def checksum():
-    global total;
-    counter = 0;
-    for i, char in enumerate(fileArray):
-        if char == ".":
-            return
-        total += counter * int(char)
-        counter += 1
+    global total
+    counter = 0
+
+    for block in fileArray:
+        if "." in block:
+            # Dots get skipped, but the counter does still increase, apparently
+            counter += len(block)
+
+        numbers = re.findall(r"(\d+\-)", block)
+        numbers = [int(number.replace("-", "")) for number in numbers]
+        for number in numbers:
+            sum = counter * number
+            total += sum
+            counter += 1
 
 with open("2024/09/input.txt") as f: 
     for line in f:
         createBlockArray(line)
-        sortfileString()
+        printFileStorage()
+        sortFileArray()
+        printFileStorage()
         checksum()
         print(total)