Problems from 2021 ICPC North America Division Championships

	Submissions				Users
Name	Total	Acc.	Ratio	Fastest	Total	Acc.	Ratio	Difficulty
Alien Microwave	295	112	38%	0.00	147	105	71%	6.7
Another Substring Query Problem	1141	228	20%	0.18	250	112	45%	8.4
Borders	433	114	26%	0.00	150	97	65%	7.2
Circle of Friends	261	70	27%	0.15	63	46	73%	6.7
Finding Polly	247	58	23%	0.48	39	22	56%	8.1
Investigating Imposters	904	277	31%	0.00	270	189	70%	6.5
Laptop Sticker	3414	2142	63%	0.00	2007	1936	96%	1.4
Longest Common Substring	1273	377	30%	0.00	335	251	75%	5.2
Simple Cron Spec	757	434	57%	0.00	367	340	93%	2.0
Surveillance	155	41	26%	0.00	37	25	68%	7.3
Train Line	241	42	17%	0.57	43	24	56%	8.8
Window Shopping	28	11	39%	0.10	16	10	62%	7.7
You Be the Judge!	1821	367	20%	0.00	359	261	73%	5.7