题解 | DNA序列

import sys

def get_gc_count(seq):
    return sum([1 for c in seq if c in {'G', 'C'}])

raw_input = []
for i,line in enumerate(sys.stdin):
    raw_input.append(line.strip())
    if i == 2:
        break

dna_seq = raw_input[0]
n = int(raw_input[1])
sub_seq = dna_seq[:n]
gc_counts = get_gc_count(sub_seq)
# print(gc_counts)
res_counts = gc_counts
idx = 0
for i in range(n, len(dna_seq)):
    if dna_seq[i] in {'G', 'C'}:
        gc_counts += 1
    if dna_seq[i - n] in {'G', 'C'}:
        gc_counts -= 1
    if gc_counts > res_counts:
        idx = i - n + 1
        res_counts = gc_counts

print(dna_seq[idx : idx+n])