Sphere Online Judge (SPOJ)

list of classical problems

ID	NAME	USERS	ACC %	DIFFICULTY C I
3360	Digital Image Recognition	27	20.40
3373	Permutation Code	43	56.10
3393	Knot or Not	8	14.93
3406	Bases	68	20.23
3412	Higgs Boson	51	18.90
3414	Bora Bora	145	49.01	34 26
3415	Shrinking Polygons	232	18.96
3420	Falling Ice	7	14.58
3461	Song Contest	12	14.29
3462	The Skatepark´s New Ramps	9	14.49
3463	Robintron	6	22.22
3465	Drive through MegaCity	21	22.78
3466	Another Longest Common Subsequence Problem	6	6.67
3482	Alias	5	62.50
3483	Begin	4	10.75
3486	Elimination	70	29.17
3490	Hidden Triangle	10	26.67
3492	Braille Transcription	16	14.06	17 17
3495	The Nobel Thief	11	50.00
3533	Game on board	26	35.14
3543	Matrica	54	39.29
3582	Restaurant Tab	24	24.60
3640	Hanoi Subway System Construction	32	38.38
3641	Earthquakes	24	36.49
3642	Pretty Printing	39	21.71
3645	Farthest Headquarters	60	26.80
3646	Adventure Tourism	46	14.77
3647	Moebius	1	2.35
3678	Cattle Bruisers	88	25.91
3733	Trezor	104	52.19
3762	Bread Tree	163	13.62
3867	Who is The Boss	169	25.29
3872	Party At School	54	24.23
3884	When (You Believe)	23	8.90
3890	Rectangles Counting	175	33.61
3893	Space settlement	67	37.37
3894	Bouncing Balls	28	37.27
3895	Matrix Game	25	24.07
3900	MinCut Query	77	28.81
3901	Black and White Nim	55	43.16
3922	Mystical River	127	25.70
3926	Manhattan Wire	80	14.07
3927	Polygon on the Grid	23	30.34
3929	Different Digits	73	22.36
3935	SHIFT Operator on Matrix	190	42.29
3939	Search of Concatenated Strings	28	25.79
3941	Kth Shortest Path	25	25.74
3942	Cleaning Robot	33	64.00
3961	Journey with Pigs	133	42.15
3965	Minimax Triangulation	58	34.43