
USACO 2021 December Contest, Platinum
Problem 2. Paired Up
Contest has ended.

Log in to allow submissions in analysis mode
At Farmer John's signal, some of the cows will form pairs such that
- Every pair consists of a Holstein h and a Guernsey g whose locations are within K of each other (1≤K≤109); that is, |xh−xg|≤K.
- Every cow is either part of a single pair or not part of a pair.
- The pairing is maximal; that is, no two unpaired cows can form a pair.
It's up to you to determine the range of possible sums of weights of the unpaired cows. Specifically,
- If T=1, compute the minimum possible sum of weights of the unpaired cows.
- If T=2, compute the maximum possible sum of weights of the unpaired cows.
INPUT FORMAT (input arrives from the terminal / stdin):
The first input line contains T, N, and K.Following this are N lines, the i-th of which contains bi,xi,yi. It is guaranteed that 0≤x1<x2<⋯<xN≤109.
OUTPUT FORMAT (print output to the terminal / stdout):
The minimum or maximum possible sum of weights of the unpaired cows.SAMPLE INPUT:
2 5 4 G 1 1 H 3 4 G 4 2 H 6 6 H 8 9
SAMPLE OUTPUT:
16
Cows 2 and 3 can pair up because they are at distance 1, which is at most K=4. This pairing is maximal, because cow 1, the only remaining Guernsey, is at distance 5 from cow 4 and distance 7 from cow 5, which are more than K=4. The sum of weights of unpaired cows is 1+6+9=16.
SAMPLE INPUT:
1 5 4 G 1 1 H 3 4 G 4 2 H 6 6 H 8 9
SAMPLE OUTPUT:
6
Cows 1 and 2 can pair up because they are at distance 2≤K=4, and cows 3 and 5 can pair up because they are at distance 4≤K=4. This pairing is maximal because only cow 4 remains. The sum of weights of unpaired cows is the weight of the only unpaired cow, which is simply 6.
SAMPLE INPUT:
2 10 76 H 1 18 H 18 465 H 25 278 H 30 291 H 36 202 G 45 96 G 60 375 G 93 941 G 96 870 G 98 540
SAMPLE OUTPUT:
1893
The answer to this example is 18+465+870+540=1893.
SCORING:
- Test cases 4-7 satisfy T=1.
- Test cases 8-14 satisfy T=2 and N≤300.
- Test cases 15-22 satisfy T=2.
**Note: the memory limit for this problem is 512MB, twice the default.**
Problem credits: Benjamin Qi