题解 | #置换操作#
置换操作
https://ac.nowcoder.com/acm/contest/84773/C
C题讨论合并的段是否相邻即可
from itertools import accumulate
def f(x):
return (x+1)*x >> 1
def main():
n = int(input())
s = list(map(len,input().split("0"))); m = len(s)
if m < 3: return print(f(n))
t = [0]; t.extend(accumulate(s))
r = [0]; r.extend(accumulate(map(f,s)))
ans = r[-1]+max(f(t[i+3]-t[i]+2)-(r[i+3]-r[i]) for i in range(m-2))
gap = [f(t[i+2]-t[i]+1)-(r[i+2]-r[i]) for i in range(m-1)]
ans = max(ans,r[-1]+max(x+y for x,y in zip(accumulate(gap,max),gap[2:])))
print(ans)
main()
