AtCoder 280にChatGPTで参加してみた。B問題の例。

main.md

問題ページ: https://atcoder.jp/contests/abc280/tasks/abc280_b

問題文を適切に整形して入力する。下付け文字を"_"で表すのと、例を入れるのが重要だったりする。　　

Solve following AtCoder problem with python. 　　

Problem Statement
You are given an integer N and a sequence S=(S_1,…,S_N) of length N.

Find a sequence A=(A_1,…,A_N) of length N that satisfies the following condition for all k=1,…,N:
A_1+A_2+…+A_k=S_k.
Such a sequence A always exists and is unique.

Constraints
1≤N≤10
−10^9≤S_i≤10^9

All values in the input are integers.

Input
The input is given from Standard Input in the following format:
N
S_1… S_N

Output
Print the elements of a sequence A=(A_1,…,A_N) that satisfies all the conditions in order, separated by spaces.

Sample Input 1
3
3 4 8

Sample Output 1
3 1 4

ChatGPTからの回答

To solve this problem, we need to find a sequence A=(A1,A2,...,AN) such that A1+A2+...+Ak=Sk for all k=1,2,...,N.

We can find such a sequence by iteratively constructing it. To do this, we can start with an empty list and then add elements to it one by one.

For the first element, A1, we can simply set it to the first element of the given sequence S, which is S1.

Next, for the second element, A2, we need to find a value that satisfies the condition A1 + A2 = S2. Since we have already set A1 to S1, we can set A2 to S2 - S1.

We can continue this process to find the remaining elements of the sequence A. For the k-th element, Ak, we need to find a value that satisfies the condition A1 + A2 + ... + Ak = Sk. Since we have already found the first k-1 elements of the sequence A, we can set Ak to Sk - (A1 + A2 + ... + Ak-1).

Here is a sample implementation of this idea in Python:

# Read input
n = int(input())
S = list(map(int, input().split()))

# Initialize the empty sequence A
A = []

# Iteratively construct the sequence A
for k in range(1, n+1):
    # Compute the k-th element of A
    Ak = S[k-1] - sum(A)
    # Add the k-th element to the sequence A
    A.append(Ak)

# Print the sequence A
print(" ".join(map(str, A)))

Let's test this implementation on the first sample input. For n=3 and S=[3, 4, 8], the sequence A should be [3, 1, 4].

# Read input
n = int(input())
S = list(map(int, input().split()))

# Initialize the empty sequence A
A = []

# Iteratively construct the sequence A
for k in range(1, n+1):
    # Compute the k-th element of A
    Ak = S[k-1] - sum(A)
    # Add the k-th element to the sequence A
    A.append(Ak)

# Print the sequence A
print(" ".join(map(str, A)))

When we run this code on the input 3 4 8, we get the output 3 1 4, which is the correct answer.

We can further optimize this implementation by using a single variable to store the sum of the elements in the sequence A, instead of using the built-in sum function. This will reduce the time complexity of the algorithm from O(N^2) to O(N). Here is the optimized implementation:

# Read input
n = int(input())
S = list(map(int, input().split()))

# Initialize the empty sequence A and the sum of its elements
A = []
sum_A = 0

# Iteratively construct the sequence A
for k in range(1, n+1):
    # Compute the k-th element of A
    Ak = S[k-1] - sum_A
    # Add the k-th element to

最後のコードは書きかけだったため、最後から2番目のコードをコピペして提出→AC