Sphere Online Judge (SPOJ)

list of classical problems

ID	NAME	QUALITY	USERS	ACC %	DIFFICULTY C I
2273	Ferries		32	19.08
2275	Toil for Oil		14	28.57
2318	Overlapping Words		89	22.26
2319	Sequence		217	28.07
2323	Broken Compass		46	13.66
2325	String Distance		213	21.46
2413	Building Beacons		42	20.00
2417	Eliminate The Enemies		22	19.74
2418	Flying Frogs		61	35.05
2419	G-Line Grid	1	4	3.48
2423	Minimal Triangulations of Graphs		30	34.71
2485	Phone Lines		19	14.19
2511	Magic Program IV		27	17.99
2631	Chomp		111	45.76
2643	Starcraft I		56	21.62
2658	Art of War		17	15.48
2661	Illumination		8	3.92
2662	Put a Point in a Hyperspace		18	9.65
2709	Untitled Problem		29	16.35
2733	K Equal Digits		15	13.38
2734	Large party		37	25.13
2855	Forest		61	12.60
2877	Another understanding of Super Dice Game		66	10.25
2879	The Cow Doctor		144	33.33	17
2898	Party of Cloaked Killers		28	16.58
2903	Transportation		11	20.31
2940	Untitled Problem II		125	15.39	34
2944	Emmons		7	7.36
2962	Painting Blocks (Act I)		111	57.69
3002	Electrophoretic		14	20.00
3005	Subdividing a Land		28	33.02
3009	Revenge of Voronoi		14	30.26
3010	Castle Wall		25	19.85
3078	Copying DNA		45	19.85
3108	Charlesbert and Merangelou		72	43.41
3166	Permutation Exponentiation		34	14.92
3197	Tree Construction		64	20.10
3208	Yet Another Longest Palindrome Problem		68	13.77
3254	Guard		15	43.24
3305	Roman Patrollers		52	59.02
3307	Hex Tile Equations	1	37	43.36
3309	Bulletin Board		23	21.53
3347	Cestarine		62	28.72
3359	Stack		47	15.73
3360	Digital Image Recognition		27	20.32
3372	Round Table	1	61	44.04
3373	Permutation Code		43	56.10
3393	Knot or Not		9	16.22
3406	Bases		70	21.08
3412	Higgs Boson		51	18.90