USACO 2013 January Contest, Gold

Problem 3. Seating

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Problem 3: Seating [Travis Hance, 2012] To earn some extra money, the cows have opened a restaurant in their barn specializing in milkshakes. The restaurant has N seats (1 <= N <= 500,000) in a row. Initially, they are all empty. Throughout the day, there are M different events that happen in sequence at the restaurant (1 <= M <= 300,000). The two types of events that can happen are: 1. A party of size p arrives (1 <= p <= N). Bessie wants to seat the party in a contiguous block of p empty seats. If this is possible, she does so in the lowest position possible in the list of seats. If it is impossible, the party is turned away. 2. A range [a,b] is given (1 <= a <= b <= N), and everybody in that range of seats leaves. Please help Bessie count the total number of parties that are turned away over the course of the day. PROBLEM NAME: seating INPUT FORMAT: * Line 1: Two space-separated integers, N and M. * Lines 2..M+1: Each line describes a single event. It is either a line of the form "A p" (meaning a party of size p arrives) or "L a b" (meaning that all cows in the range [a, b] leave). SAMPLE INPUT (file 10 4 A 6 L 2 4 A 5 A 2 INPUT DETAILS: There are 10 seats, and 4 events. First, a party of 6 cows arrives. Then all cows in seats 2..4 depart. Next, a party of 5 arrives, followed by a party of 2. OUTPUT FORMAT: * Line 1: The number of parties that are turned away. SAMPLE OUTPUT (file seating.out): 1 OUTPUT DETAILS: Party #3 is turned away. All other parties are seated.
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