Sphere Online Judge (SPOJ)

list of classical problems

ID	NAME	USERS	ACC %	DIFFICULTY C I
3309	Bulletin Board	20	21.43
3314	Umnozak	109	29.38	42 17
3347	Cestarine	61	34.57
3359	Stack	45	15.60
3360	Digital Image Recognition	27	19.58
3373	Permutation Code	40	54.43
3393	Knot or Not	6	13.56
3406	Bases	68	21.12
3412	Higgs Boson	48	18.67
3414	Bora Bora	144	49.01	34 26
3415	Shrinking Polygons	232	18.97
3420	Falling Ice	7	24.14
3461	Song Contest	12	14.44
3462	The Skatepark´s New Ramps	10	32.65
3463	Robintron	6	22.22
3465	Drive through MegaCity	23	25.16
3466	Another Longest Common Subsequence Problem	6	31.58
3482	Alias	4	57.14
3483	Begin	4	11.11
3486	Elimination	67	28.48
3490	Hidden Triangle	9	28.85
3492	Braille Transcription	16	14.40	17 17
3495	The Nobel Thief	6	38.10
3533	Game on board	28	36.73
3543	Matrica	53	39.38
3582	Restaurant Tab	24	27.27
3640	Hanoi Subway System Construction	32	41.75
3641	Earthquakes	23	37.68
3642	Pretty Printing	39	24.38
3645	Farthest Headquarters	56	25.93
3646	Adventure Tourism	45	15.69
3647	Moebius	1	2.56
3678	Cattle Bruisers	87	25.75
3733	Trezor	102	52.72
3762	Bread Tree	162	13.54
3867	Who is The Boss	167	25.03
3872	Party At School	50	23.87
3884	When (You Believe)	23	8.98
3890	Rectangles Counting	175	33.61
3893	Space settlement	65	38.12
3894	Bouncing Balls	27	37.74
3895	Matrix Game	25	31.71
3900	MinCut Query	77	28.78
3901	Black and White Nim	55	44.50
3922	Mystical River	127	25.47
3926	Manhattan Wire	81	14.32
3927	Polygon on the Grid	22	36.62
3929	Different Digits	71	21.97
3935	SHIFT Operator on Matrix	189	42.19
3939	Search of Concatenated Strings	27	25.64