505. 火柴排队 - AcWing题库

n=int(input())
a=list(map(int,input().split()))
b=list(map(int,input().split()))
mod=99999997
# map
c=[0 for i in range (n+1)]
# 归并排序模板

def _MergeSort(arr,l,r,tmp):
    if  l>=r: return 0
    # 分治思想
    mid=l+r>>1
#     当前层操作
    res=(_MergeSort(arr,l,mid,tmp))+(_MergeSort(arr,mid+1,r,tmp))%mod
#     当前层逻辑
    begin1=l
    end1=mid
    begin2=mid+1
    end2=r
    index=l

    while(begin1<=end1 and begin2<=end2):
        if arr[begin1]<arr[begin2]:
            tmp[index]=arr[begin1]
            index+=1
            begin1+=1
        else:
            tmp[index]=arr[begin2]
            index+=1
            begin2+=1
            res=(res+end1-begin1+1) % mod

#    把多余的添加到数组
    # 把多余的添加到数组
    while begin1 <= end1:
        tmp[index] = arr[begin1]
        index += 1
        begin1 += 1
    while begin2 <= end2:
        tmp[index] = arr[begin2]
        index += 1
        begin2 += 1

    for i in range (l,r+1):
        arr[i]=tmp[i]
    return res

def MergeSort(arr):
    tmp=[0 for _ in range (len(arr))]
    # 调用子函数
    res=_MergeSort(arr,0,len(arr)-1,tmp)
    return res

# 离散化
def work(a):
    n=len(a)
    p= [i for i in range (1,n+1)]
    p.sort(key=lambda x:a[x-1])
    for i in range (1,n+1):
        a[p[i-1]-1]=i

work(a)
work(b)
# hash map
for i in range(n):
    c[a[i]]=i
for i in range (n):
    b[i]=c[b[i]]
print(MergeSort(b))