A Hybrid alldifferent-Tabu Search Algorithm for Solving Sudoku Puzzles

Table 1

Difficulty of tested instances.

Authors	Difficulty groups
	Easy	Medium	Difficult	Most difficult
[26]	1, 2	3, 4, 5	—	—
	E	C, D	SD	—
[27]	Easy	Medium	Hard	—
[28]	—	—	—	AI Escargot