AtCoder Beginner Contest 159 Participation Report

AtCoder Beginner Contest 159 Participation Report

ABC159A - The Number of Even Pairs

Break through in 3 and a half minutes. Odd or even pairs are the answer. If you know k </ sub> C 2 </ sub> = k (k-1) / 2 The rest is just writing, but it's difficult for A problem, this.

N, M = map(int, input().split())

print(N * (N - 1) // 2 + M * (M - 1) // 2)

ABC159B - String Palindrome

Break through in 12 minutes. It took too long orz. Write a check routine, then convert 1-indexed to 0-indexed and check as told. It's difficult for B problem, isn't it? this.

S = input()


def is_palindrome(s):
    return s == s[::-1]


N = len(S)

if not is_palindrome(S):
    print('No')
    exit()

if not is_palindrome(S[:(N - 1) // 2]):
    print('No')
    exit()

if not is_palindrome(S[(N + 3) // 2 - 1:]):
    print('No')
    exit()

print('Yes')

ABC159C - Maximum Volume

Break through in 2 minutes. A Isn't this a mistake?

L = int(input())

print((L / 3) ** 3)

ABC159D - Banned K

Break through in 10 minutes. Of course, if you recalculate all the numbers when the kth ball is excluded, TLE. For the time being, calculate the number when you do not pull out, and adjust the number for the kth value and answer. ..

N = int(input())
A = list(map(int, input().split()))

d = {}
for a in A:
    if a in d:
        d[a] += 1
    else:
        d[a] = 1

s = 0
for k in d:
    s += d[k] * (d[k] - 1) // 2

for i in range(N):
    t = d[A[i]]
    print(s - t * (t - 1) // 2 + (t - 1) * (t - 2) // 2)

ABC159E - Dividing Chocolate

Lost. Cumulative sum reduced the number of white chocolates from * O * (* HW ) to * O * ( H *) and brute force with recursive function, but it was TLE & WA. So there is a bug in the implementation somewhere ...

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