코딩테스트 때 쓰이는 문법 모음! 💕

heap - 힙 ✔️

import heapq # 기본은 min-heap, max-heap 사용시 -값 넣기

lst = [1, 2, 3]
heapq.heapify(lst)
# 빈 배열은 push시 자동으로 힙으로 됨
empty = []

💡 삽입 / 제거 / 조회

heapq.heappop(my_list)
heapq.heappush(my_list, -1)
my_list[0]

---

queue - 큐 ✔️

from collections import deque
que = deque([1, 2, 3])

💡 원소 중간 삽입

que.insert(i, num)

💡 삽입 / 제거 / 조회

que.append(item)
que.popleft()
que[0]

---

counter ✔️

import collections
my_list = ["a", "a", "b", "b", "c"]
collections.Counter(my_list)

# Counter({'a': 2, 'b': 2, 'c': 1})

---

itertools ✔️

import itertools
from itertools import permutations
from itertools import combinations
from itertools import product
from itertools import chain

---

💡 permutations - 순열

permutations(range(1, 10), 3)
permutations(lst)

💡 combinations - 조합

combinations('ABC', 2)

💡 product - 중복순열

product(range(1,n1+1), range(1,n2+1), range(1,n3+1))

or_not = [(0, 500), (0, 1500)]
list(product(*or_not))

#[(0,0), (0,1500), (500,0), (500,1500)]

💡 chain - flatten(2차배열 ->1차배열)

itertools.chain(*board)
chain(*board)

---

dictionary - 해시 ✔️

💡 get

my_dict['total']
my_dict.get('total', 0)

💡 제거 - pop : 키가 없는 경우 default 리턴

my_dict.pop('홍길동', 180)

💡 탐색

dict.items()
dict.keys()
dict.values()

💡 그래프 셋팅 : get 사용

nodes = {}
for v1, v2 in edge:
    nodes[v1] = nodes.get(v1, []) + [v2]
    nodes[v2] = nodes.get(v2, []) + [v1]

💡 그래프 셋팅 with dist : get 사용

nodes = {}
for v1, v2, d in road:
    nodes[v1] = nodes.get(v1, []) + [(v2, d)]
    nodes[v2] = nodes.get(v2, []) + [(v1, d)]

💡 그래프 셋팅 거리 초기화

dist = { i:float('inf') if i != 1 else 0 for i in range(1, N+1) }

---

defaultdict ✔️

from collections import defaultdict

dict1 = defaultdict(set)
dict2 = defaultdict(list)
dict3 = defaultdict(int) -> 0으로 셋팅

💡 그래프 셋팅 : defaultdict 사용

from collections import defaultdict
nodes = defaultdict(list)
for v1, v2 in edge:
    nodes[v1].append(v2)
    nodes[v2].append(v1)

---

set - 셋 ✔️

💡 삽입 / 제거

my_set.add(3)
my_set.remove(3)

💡 include

if 3 in my_set:
	print('3 있음')
if 3 not in my_set:
	print('3 없음')

💡 합집합, 교집합, 차집합

set1 | set2
set1.update(set2)

set1 - set2

set1 & set2

---

bisect ✔️

from bisect import bisect_left, bisect_right

💡 최소값 바로 왼쪽 (최소값 들어갈 index)

bisect_left(lst, start)

💡 최대값 바로 오른쪽 (최대값 들어갈 index)

bisect_right(lst, end)

💡 count_by_lange

def count_by_lange(lst, start, end):
    return bisect_right(lst, end) - bisect_left(lst, start)

---

DELTA - 방향 ✔️

DELTAS = [(0, 1), (0, -1), (-1, 0), (1, 0)] # 오른쪽 왼쪽 위 아래
DELTAS = [(-1, 0, UP), (1, 0, DOWN), (0, 1, RIGHT), (0, -1, LEFT)]
DELTAS = {'U':(0, 1), 'D':(0, -1), 'L':(-1, 0), 'R':(1, 0)}

DELTAS = {'U': (-1, -1), 'D': (1, 0), 'R': (0, 1)}
NEXT = {'U': 'D', 'D': 'R', 'R': 'U'}

---

visitable - 탐색 범위 확인 ✔️

def visitable(y, x, m, n):
    return 0 <= y < m and 0 <= x < n

---

소수 ✔️

N, primes = end_num, set()
prime_check = [False, False] + [True]*(N-1)

for i in range(2, N+1):
    if prime_check[i]:
        primes.add(i)
        prime_check[i*2::i] = [False] * len(prime_check[i*2::i])

---

최소공배수 / 최대공약수 ✔️

💡 최대공약수

from fractions import gcd
gcd(6,8) # 2

💡 최소공배수

def lcm(a,b):
    return  a * b // gcd(a, b)

---

곱으로 나타내기 ✔️

[(number//i, i) for i in range(1, int(number**.5)+1) if number % i == 0]
# number = 24 -> 곱해서 24가되는 경우
[(24, 1), (12, 2), (8, 3), (6, 4)]

---

이분탐색 ✔️

💡 최소값

def impossible(n, middle, times):
    return sum([middle // x for x in times]) < n

def solution(n, times):
    left, right = 1, max(times)*n
    while left < right:
        middle = (left + right) // 2
        if impossible(n, middle, times): 
            left = middle + 1
        else: 
            right = middle
    return left

💡 최대값

def is_poss(middle, budgets, M):
    return M >= sum([min(middle, budget) for budget in budgets])

def solution(budgets, M):
    left, right = 1, max(budgets)
    while left < right:
        middle = (left + right + 1) // 2 
        if is_poss(middle, budgets, M):
            left = middle
        else:
            right = middle - 1
    return right

---

sort ✔️

💡 sort

lst.sort()
dist.sort(reverse=True)
lst.sort(key= lambda x : (x*4)[:4], reverse=True)

💡 sorted

sorted(lst)
sorted(lst, reverse=True)
sorted(answer, key = lambda x : (x[0], -x[1], x[2]))

---

count ✔️

💡 요소 개수 세기

lst.count(0)
[*row, *col, *diag].count(n)

💡 filter count

filter = [item for item in items if 조건식 ]
len(filter)

---

2차배열 ✔️

💡 초기화 m * n 행렬

board = [[0] * n for i in range(m)]

💡 행열 뒤집기 (n*m)

reversed = list(map(list,zip(*board)))

💡 90도 회전

def rotate90(arr):
    return list(zip(*arr[::-1]))

---

string ✔️

💡 글자 replace

query.replace('?','a')

💡 기준으로 쪼개기

s.split("},{")

💡 join

number = int(''.join(x))

💡 string 갯수 단위로 쪼개기

splited = [s[i:i+size] for i in range(0, LENGTH, size)]
# size = 3 : aabbaccc -> ['aab', 'bac', 'cc']

---

정규식

import re

💡 찾기

re.search("^"+pre+".+",number)
re.findall(query, word)
lst = re.findall('\d+',s)
# ['2', '2', '1', '3', '4']
re.compile("(\D)")

---

원형 선형으로 ✔️

weak_point = weak + [w+n for w in weak]

---

math ✔️

import math

💡 ceil

math.ceil(num / div)

💡 factorial

math.factorial(3)