ABC451をPythonで（A～E）

AtCoder Beginner Contest 451の解答等の速報的まとめ

A問題

問題文のまま

A

print("No" if len(input()) % 5 else "Yes")

B問題

集計して差を出力

B

n, m = map(int, input().split())
now = [0] * m
nxt = [0] * m
for _ in range(n):
    a, b = map(lambda x:int(x) - 1, input().split())
    now[a] += 1
    nxt[b] += 1

for a_i, b_i in zip(now, nxt):
    print(b_i - a_i)

C問題

SortedListにぶち込む
各要素は高々2回しか触らないので間に合う

C

from sortedcontainers import SortedList

s = SortedList([])

for _ in range(int(input())):
    com, h = map(int, input().split())
    if com == 1:
        s.add(h)
    else:
        while s and s[0] <= h:
            s.pop(0)
    print(len(s))

D問題

長さを見つつDFSで９桁以下の数をすべて作成

D

lst = list()
keta = 0
x = 1
while x < 10 ** 9:
    lst.append(str(x))
    x *= 2

s = set()
def dfs(now):
    global s
    for l_i in lst:
        nxt = now + l_i
        if len(nxt) <= 9:
            s.add(int(nxt))
            if len(nxt) <= 8:
                dfs(nxt)

dfs("")
ans = sorted(s)
print(ans[int(input()) - 1])

E問題

選ぶ辺は距離が短いほうからループにならない$N-1$本の辺
各頂点からDFSで条件を満たすか判定

E

from collections import deque


class UnionFind:
    """
    URL : https://note.nkmk.me/python-union-find/
    """
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)


n = int(input())
data = list()
for i in range(n - 1):
    a = list(map(int, input().split()))
    for j, a_i in enumerate(a, i + 1):
        data.append((a_i, i, j))

data.sort()

UF = UnionFind(n)
edge = [list() for _ in range(n)]
cnt = 0
for w_i, i, j in data:
    if not UF.same(i, j):
        UF.union(i, j)
        edge[i].append((j, w_i))
        edge[j].append((i, w_i))
        cnt += 1

    if cnt >= n - 1:
        break

dist = list()
for start in range(n):
    check = [False] * n
    dist_i = [-1] * n
    q = deque()
    q.append(start)
    check[start] = True
    dist_i[start] = 0
    while q:
        now = q.popleft()
        for to, w_to in edge[now]:
            if check[to]:
                continue
            dist_i[to] = dist_i[now] + w_to
            check[to] = True
            q.append(to)

    dist.append(dist_i)

ans = "Yes"
for w_i, i, j in data:
    if dist[i][j] != w_i:
        ans = "No"

print(ans)