aoc2024

commit 303748ab9224157ee7e752a192a7a9ff96fa167b
parent aa290e46f19c74bb34de33e5f7b2bf91da81f8c0
Author: Martin Ashby <martin@ashbysoft.com>
Date:   Tue, 31 Dec 2024 01:34:12 +0000

Day 9 pt2

Diffstat:
A
src/main/java/day9_pt2.java
 | 
59
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 59 insertions(+), 0 deletions(-)
diff --git a/src/main/java/day9_pt2.java b/src/main/java/day9_pt2.java
@@ -0,0 +1,59 @@
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.io.IOException;
+import java.util.*;
+import java.util.stream.*;
+
+public class day9_pt2 {
+  public static void main(String[] args) throws IOException {
+      var input = Files.readString(Path.of(args[0]));
+      var dm = new ArrayList<Integer>();
+      int label = 0;
+      boolean block = true;
+      var it = input.chars().iterator();
+      while (it.hasNext()) {
+        var ct = it.next() - '0';
+        var add = block ? label : -1;
+        for (int i=0;i<ct;i++) dm.add(add);
+        label += block ? 1 : 0;
+        block = !block;
+      }
+      label--;
+      //System.out.printf("dm [%s]\n", dm);
+      
+
+      while (label >= 0) {
+        var fStart = dm.indexOf(label);
+        var fEnd = dm.lastIndexOf(label)+1;
+        var fLen = fEnd-fStart;
+        
+        // find first free space
+        var sStart = 0;
+        while (sStart < dm.size() && dm.get(sStart) != -1) sStart++;
+        
+        while (sStart < dm.size() && sStart < fStart) {
+          var sEnd = sStart;
+          while (dm.get(sEnd) == -1) sEnd++;  
+          var sLen = sEnd-sStart;
+          if (sLen >= fLen) {
+            //System.out.printf("moving label %d sLen %d sStart %d sEnd %d fStart %d fEnd %d\n", label, sLen, sStart, sEnd, fStart, fEnd);
+            for (var j=sStart; j<sStart+fLen; j++) dm.set(j, label);
+            for (var j=fStart; j<fEnd; j++) dm.set(j, -1);
+            break;
+          } else {
+            // space wasnt big enough, find the next free space
+            sStart = sEnd;
+            while (sStart < dm.size() && dm.get(sStart) != -1) sStart++;
+          }
+        }
+        label--;
+      }
+      //System.out.printf("dm [%s]\n", dm);
+      long ck = 0;
+      for (int i=0;i<dm.size();i++){
+        long ch = dm.get(i);
+        if (ch != -1) ck += (long)i * ch;
+      }
+      System.out.printf("day9, pt2: %d\n", ck);
+  }
+}