csp202109-2 非零段划分 满分AC python

n=int(input())
list1=[0]+[int(x) for x in input().split()]+[0]
xh=sorted(set(list1))
dic={}
for x in range(1,len(list1)-1):
    if list1[x] in dic:
        dic[list1[x]].append(x)
    else:
        dic[list1[x]]=[x]
pri=0
num=0
for x in range(len(list1)-1):
    if list1[x]==0 and list1[x+1]>0:
        num+=1
for x in xh:
    if x==0:
        continue
    for y in dic[x]:
        list1[y]=0
        if list1[y+1]>0 and list1[y-1]>0:
            num+=1
            
        elif list1[y+1]==0 and list1[y-1]==0:
            num-=1
    pri=max(pri,num)
print(pri)