From cb2935e0f5139efeea90f06d7c3c9e752a223bc3 Mon Sep 17 00:00:00 2001
From: mike <michael@appmodel.nl>
Date: Wed, 14 Jan 2026 10:24:55 +0100
Subject: [PATCH] introduce bitloops

---
 src/main/java/puzzle/SwedishGenerator.java | 94 +++++++++++-----------
 1 file changed, 46 insertions(+), 48 deletions(-)

diff --git a/src/main/java/puzzle/SwedishGenerator.java b/src/main/java/puzzle/SwedishGenerator.java
index c0ab69a..5068b3a 100644
--- a/src/main/java/puzzle/SwedishGenerator.java
+++ b/src/main/java/puzzle/SwedishGenerator.java
@@ -789,61 +789,59 @@ public record SwedishGenerator(Rng rng, int[] stack, Clues cache) {
       return cross * 10 + s.length();
    }
    static boolean placeWord(Grid grid, Slot s, long w, long[] undoBuffer, int offset) {
-      long maskLo = 0, maskHi = 0;
-      int  i      = 0;
       if (s.increasing()) {
-         for (long b = s.lo; b != 0; b &= b - 1, i++) {
-            int  idx = Long.numberOfTrailingZeros(b);
-            byte cur = grid.letter32At(idx), ch = Lemma.byteAt(w, i);
-            if (cur == DASH) {
-               maskLo |= (1L << idx);
-               grid.setLetterLo(idx, ch);
-            } else if (cur != ch) {
-               grid.undoPlace(maskLo, maskHi);
-               return false;
-            }
+         for (long b = s.lo & grid.lo; b != 0; b &= b - 1) {
+            int idx = Long.numberOfTrailingZeros(b);
+            if (grid.g[idx] != Lemma.byteAt(w, Long.bitCount(s.lo & ((1L << idx) - 1)))) return false;
          }
-         for (long b = s.hi; b != 0; b &= b - 1, i++) {
-            int  idx = 64 | Long.numberOfTrailingZeros(b);
-            byte cur = grid.letter32At(idx), ch = Lemma.byteAt(w, i);
-            if (cur == DASH) {
-               maskHi |= (1L << (idx & 63));
-               grid.setLetterHi(idx, ch);
-            } else if (cur != ch) {
-               grid.undoPlace(maskLo, maskHi);
-               return false;
-            }
+         int bcLo = Long.bitCount(s.lo);
+         for (long b = s.hi & grid.hi; b != 0; b &= b - 1) {
+            int idx = Long.numberOfTrailingZeros(b);
+            if (grid.g[64 | idx] != Lemma.byteAt(w, bcLo + Long.bitCount(s.hi & ((1L << idx) - 1)))) return false;
          }
+         
+         long maskLo = s.lo & ~grid.lo, maskHi = s.hi & ~grid.hi;
+         if ((maskLo | maskHi) != 0) {
+            for (long b = maskLo; b != 0; b &= b - 1) {
+               int idx = Long.numberOfTrailingZeros(b);
+               grid.g[idx] = Lemma.byteAt(w, Long.bitCount(s.lo & ((1L << idx) - 1)));
+            }
+            for (long b = maskHi; b != 0; b &= b - 1) {
+               int idx = Long.numberOfTrailingZeros(b);
+               grid.g[64 | idx] = Lemma.byteAt(w, bcLo + Long.bitCount(s.hi & ((1L << idx) - 1)));
+            }
+            grid.lo |= maskLo;
+            grid.hi |= maskHi;
+         }
+         undoBuffer[offset << 1]       = maskLo;
+         undoBuffer[(offset << 1) | 1] = maskHi;
       } else {
-         for (long b = s.hi; b != 0; i++) {
-            int  msb = 63 - Long.numberOfLeadingZeros(b);
-            int  idx = 64 | msb;
-            byte cur = grid.letter32At(idx), ch = Lemma.byteAt(w, i);
-            if (cur == DASH) {
-               maskHi |= (1L << msb);
-               grid.setLetterHi(idx, ch);
-            } else if (cur != ch) {
-               grid.undoPlace(maskLo, maskHi);
-               return false;
-            }
-            b &= ~(1L << msb);
+         int bcHi = Long.bitCount(s.hi);
+         for (long b = s.hi & grid.hi; b != 0; b &= b - 1) {
+            int idx = Long.numberOfTrailingZeros(b);
+            if (grid.g[64 | idx] != Lemma.byteAt(w, Long.bitCount(s.hi & ~((1L << idx) | ((1L << idx) - 1))))) return false;
          }
-         for (long b = s.lo; b != 0; i++) {
-            int  msb = 63 - Long.numberOfLeadingZeros(b);
-            int  idx = msb;
-            byte cur = grid.letter32At(idx), ch = Lemma.byteAt(w, i);
-            if (cur == DASH) {
-               maskLo |= (1L << msb);
-               grid.setLetterLo(idx, ch);
-            } else if (cur != ch) {
-               grid.undoPlace(maskLo, maskHi);
-               return false;
-            }
-            b &= ~(1L << msb);
+         for (long b = s.lo & grid.lo; b != 0; b &= b - 1) {
+            int idx = Long.numberOfTrailingZeros(b);
+            if (grid.g[idx] != Lemma.byteAt(w, bcHi + Long.bitCount(s.lo & ~((1L << idx) | ((1L << idx) - 1))))) return false;
          }
+         
+         long maskLo = s.lo & ~grid.lo, maskHi = s.hi & ~grid.hi;
+         if ((maskLo | maskHi) != 0) {
+            for (long b = maskHi; b != 0; b &= b - 1) {
+               int idx = Long.numberOfTrailingZeros(b);
+               grid.g[64 | idx] = Lemma.byteAt(w, Long.bitCount(s.hi & ~((1L << idx) | ((1L << idx) - 1))));
+            }
+            for (long b = maskLo; b != 0; b &= b - 1) {
+               int idx = Long.numberOfTrailingZeros(b);
+               grid.g[idx] = Lemma.byteAt(w, bcHi + Long.bitCount(s.lo & ~((1L << idx) | ((1L << idx) - 1))));
+            }
+            grid.lo |= maskLo;
+            grid.hi |= maskHi;
+         }
+         undoBuffer[offset << 1]       = maskLo;
+         undoBuffer[(offset << 1) | 1] = maskHi;
       }
-      undoBuffer[offset << 1]       = maskLo;
-      undoBuffer[(offset << 1) | 1] = maskHi;
       return true;
    }