readme

Profiles

hackerrank
UVa Online Judge
freeCodeCamp.org

Problems by cases

문제 분류 - 알고리즘별, 시간 복잡도별, 자료구조별.
비슷한 문제를 모아놓음.

Code

알고리즘별 코드.
수학 - Prime number등.
기타 - 이분탐색 등.

My solutions

hackerrank
UVa Online Judge
USACO_Training_Program
programmers

memo

javascript

• counter

  let arr=[1,2,3,1,2,1,3,1,1,1,1]
  
  const counter = arr => arr.reduce((cnt, v) => {
    cnt[v] = (cnt[v] || 0) + 1
    return cnt
  }, {} )
  
  console.log(counter(arr))

  python

• loop without for, while

  print(*map(lambda x: x*x,range(9)), sep='\n')

  print(*range(1,9), sep='',end='')

• list comprehension

  [[i,j] for i in range(9) for j in range(9) if i+j!=5]

  print(*[str(i)+'x'+str(j)+'='+str(i*j) for i in range(2,10) for j in range(2,10) if i<=j])

• using Counter

  import collections
  a=collections.Counter([1,2,3,4,5])
  b=collections.Counter([1,2,3,4])
  a-=b
  print([*a][0])

• sort with multi keys

  name=["B","A","C","B","C"]
  score=[52,51,51.5,50,51]
  total=[*zip(name,score)]
  total.sort(key=lambda p:(-p[1],p[0]))#by tuple
  print(total)

• insert sort

  import bisect
  sortedArr=[100,200,300,400,500,600,700]
  bisect.insort(sortedArr,550)
  bisect.insort(sortedArr,0)
  bisect.insort(sortedArr,1000)
  print(sortedArr)

• bit counter

  n=31
  b=bin( n )
  print(b.count('1'))

• number of True

  strs=['aa','BB','cC','dd']
  print( sum(map(str.islower,strs)))

• permultation & combination

  #순서무관 : 뽑는 순서는 상관이 없다.
  #순서상관 : 뽑는 순서가 다르면 다른경우다.    
  import itertools
  n=5
  r=3
  arr=[*range(0,n)]
  itertools.product(arr,repeat=r)#중복순열 : 순서상관, 중복허용
  itertools.permutations(arr,r)#순열 : 순서상관, 중복안됨
  itertools.combinations(arr,r)#조합 : 순서무관, 중복안됨
  itertools.combinations_with_replacement(arr,r)#중복 조합 : 순서무관, 중복허용

• datetime from string and to string

  import datetime
  r=datetime.datetime.strptime("2019-09-17 11:11:11.111","%Y-%m-%d %H:%M:%S.%f")
  print(r)
  t=r-datetime.timedelta(seconds=0.999)
  print(t)
  print(datetime.datetime.strftime(t,"%Y-%m-%d %H:%M:%S.%f"))

  c

• modulo big integer

  #include<stdio.h>
  int bigmod(char *num,int m){
      int ret=0;
      while(*num){
          ret=(ret*10+(*num)-'0')%m;
          num++;
      }
      return ret;
  }
  int main() {
      char num[1000]="324842959490294584920434765756745534524235445";
      int m=32854;
      printf("%d\n",bigmod(num,m));
  }

• [set]

  #include<stdio.h>
  int main()
  {
      char st[100];
      scanf("%[^\n]%*c", st);
      printf("%s",st);
      scanf("%[^\n]s", st);
      printf("%s",st);
  }

regular expresion

• /(ok){3,}/
okokok, okokokok, etc.

• /(\d)\1/
  true : 11, 22
  false : 12, 23
/(\d)\1/ not eq /\d\d/

• /(?<=a)x(?=b)/ : lookbehind, lookahead
  select x after a and before b

add value on last

//javascript
a=[]//array object
a.push(1)
a.push(2)
a.push(3)

#python
a=[]#list
a.append(1)
a.append(2)
a.append(3)

spread operator

#python
a=[1,2]
c=[5,6,*a]

//javascript
a=[1,2]
c=[5,6,...a]