Ciao Dario,
molto probabilmente c'è stato qualche problema nella richiesta del "HINT". Difficiile da individuare l'origine del problema.
Questi sono i suggerimenti come dovevano essere dati:
+;3;r6c3;hidden single 3 in block 4, in r6c3;
+;7;r8c5;hidden single 7 in block 8, in r8c5;
+;3;r8c4;hidden single 3 in block 8, in r8c4;
+;8;r3c9;8 hidden single in row 3, in r3c9;
+;8;r8c7;hidden single 8 in block 9, in r8c7;
+;8;r7c2;hidden single 8 in block 7, in r7c2;
+;1;r2c4;1 hidden single in column 4, in r2c4;
+;9;r1c4;hidden single 9 in block 2, in r1c4;
+;2;r9c4;2 last digit in column , r2c4;
+;2;r1c6;2 naked single in cell r1c6;
+;8;r2c6;8 naked single in cell r2c6;
+;8;r9c5;hidden single 8 in block 8, in r9c5;
-;7;r2c2;INTERSECTION - in block 4 is present only on column 2 - deleting 7 from 22;
-;7;r2c8;INTERSECTION - in block 6 is present only on column 8 - deleting 7 from 28;
-;3;r3c1;XY-WING, number 673 in cells 19,38,11 - deleting 3 from 31;
+;3;r3c8;3 hidden single in row 3, in r3c8;
+;6;r3c2;6 hidden single in row 3, in r3c2;
+;1;r3c1;1 last digit in row , r3c2;
+;1;r9c9;1 hidden single in row 9, in r9c9;
+;1;r5c3;1 hidden single in row 5, in r5c3;
+;1;r8c2;hidden single 1 in block 7, in r8c2;
+;9;r8c1;hidden single 9 in block 7, in r8c1;
+;9;r6c2;hidden single 9 in block 4, in r6c2;
+;7;r4c2;hidden single 7 in block 4, in r4c2;
+;2;r2c2;2 last digit in column , r5c3;
+;2;r4c3;hidden single 2 in block 4, in r4c3;
+;5;r5c1;5 last digit in block , r5c3;
+;7;r6c8;hidden single 7 in block 6, in r6c8;
+;1;r4c8;hidden single 1 in block 6, in r4c8;
+;1;r6c5;hidden single 1 in block 5, in r6c5;
+;4;r4c5;4 last digit in block , r5c3;
+;5;r4c7;5 last digit in row , r5c3;
etc