Let p0=p2024=0 and let t be a positive integer such that pt=2023. The given condition gives
2=4048−(2023+2023)=(p1+i=1∑2022∣pi+1−pi∣+p2023)−(i=0∑t−1(pi+1−pi)+i=t∑2023(pi−pi+1))=(i=0∑t−1∣pi+1−pi∣+i=t∑2023∣pi−pi+1∣)−(i=0∑t−1(pi+1−pi)+i=t∑2023(pi−pi+1))=i=0∑t−1(∣pi+1−pi∣−(pi+1−pi))+i=t∑2023(∣pi−pi+1∣−(pi−pi+1)),
thus
f(i)={pi+1−pipi−pi+1(0≤i≤t−1),(t≤i≤2023)
satisfies ∑i=02023(∣f(i)∣−f(i))=2. Since we have
∣a∣−a={02∣a∣(a≥0),(a<0)
for any integer a, ∑i=02023(∣f(i)∣−f(i))=2 if and only if there exists an integer k with 0≤k≤2023 such that f(k)=−1 and f(i)>0 for every integer i which is different from k and 0≤i≤2023. Since f(0), f(t−1), f(t) and f(2023) are all positive, k is neither 0, t−1, t nor 2023.
When k≥t+1, we have 0=p0<p1<⋯<pt>pt+1>⋯>pk<pk+1>pk+2>⋯>p2024=0 with pk+1=pk+1. Since pk+1<2023, we have pk=pk+1−1≤2021. Let (A,B) be a pair of sets satisfying A∩B=∅, A∪B={1,2,…,m−1,m+2,m+3,…,2022} for some integer m with 1≤m≤2021. We fix such a pair (A,B), and consider all permutations p1,p2,…,p2023 that satisfy the following conditions:
∙{p1,p2,…,pt−1}=A,
∙pt=2023, pk=m, pk+1=m+1,
∙{pt+1,pt+2,…,pk−1,pk+2,pk+3,…,p2023}=B
The number of such permutations is to be determined. Note that p1,p2,…,pt−1 are arranged in increasing order of elements in A. The numbers pt+1,pt+2,…,pk−1 are arranged in decreasing order of the elements in B that are greater than m, and the numbers pk+2,pk+3,…,p2023 are arranged in decreasing order of the elements in B that are less than m+1. Therefore, pt+1,pt+2,…,pk−1,pk+2,pk+3,…,p2023 are arranged in decreasing order of elements in B. Conversely, this permutation satisfies all the conditions, hence we conclude that there is exactly one such permutation. Since there are 2021 choices for m, and 22020 choices for (A,B), there are 2021⋅22020 permutations satisfying the conditions when k≥t+1.
By the same reasoning, the number of permutations satisfying the conditions when k≤t−2 is also 2021⋅22020. Thus, the answer is 2021⋅22020⋅2=2021⋅22021.