Sphere Online Judge (SPOJ)

list of classical problems

ID	NAME	USERS	ACC %	DIFFICULTY C I
3961	Journey with Pigs	130	42.94
3965	Minimax Triangulation	58	34.60
3970	Convert to Decimal Base System	53	38.60	17 17
3972	Stargates	45	13.29
3981	Shortest Regular Bracket	79	35.74
4003	Subway planning	40	18.08
4004	Exploding CPU	141	46.17
4008	Con Voi	9	56.00
4010	Chặt cây	8	39.13
4021	Bipalindrome	183	30.89
4034	Pizza Delivery	53	17.10
4052	Game	75	33.70
4060	A game with probability	197	21.61
4062	Rob Mini-Safe	112	39.35
4069	Morphing is Fun	29	20.69
4070	Two Professors	101	14.40
4083	Tele Broadcast	67	50.52
4097	Locomotive	34	44.30
4142	Ellipse	17	8.46
4154	IZBORI	36	24.54
4156	PLAHTE	65	36.36
4160	A1 Road	86	50.46
4178	Distance on a square lattice	122	54.32
4185	Cube	52	35.93
4188	Amazing equality	38	13.58
4189	Landing	4	3.64
4202	Brackets Parade	232	44.26
4210	Fast Maximum Matching	10	41.94
4211	Fast Maximum Flow	16	22.22
4212	Another Longest Increasing Subsequence Problem	11	48.15
4225	Payment System	30	66.67
4275	rotate it	40	55.70
4278	Battlefield	5	44.00
4307	Stamps	27	40.00
4308	Byteantean towns	55	24.22
4309	Circular game	32	19.89
4311	Quasi-template	54	33.92
4324	The fate of the pineapple	40	28.41
4361	Connected Points	9	52.17
4378	Twofive	63	32.26
4407	Counting Arborescence	100	34.02
4410	Repair the Door	58	22.49
4411	Counting Expressions	29	42.47
4414	Highway	53	21.89
4420	Counting Graphs	58	34.93
4421	Irreducible polynomials over GF2	62	18.01
4453	Bouncing Balls II	219	27.73
4455	Going to the Movies	86	36.33
4459	Muzidabutur	4	21.43
4461	A Famous Airport Manager	23	16.36