List Comprehensions for文 if文

・問題

Let's learn about list comprehensions! You are given three integers  and  representing the dimensions of a cuboid along with an integer . You have to print a list of all possible coordinates given by  on a 3D grid where the sum of is not equal to . Here, 

Input Format

Four integers  and  each on four separate lines, respectively.

Constraints

Print the list in lexicographic increasing order.

Sample Input 0

1
1
1
2

Sample Output 0

[[0, 0, 0], [0, 0, 1], [0, 1, 0], [1, 0, 0], [1, 1, 1]]

Explanation 0

Concept

You have already used lists in previous hacks. List comprehensions are an elegant way to build a list without having to use different for loops to append values one by one. This example might help.

Example: You are given two integers x and y . You need to find out the ordered pairs ( i , j ) , such that ( i + j ) is not equal to n and print them in lexicographic order.( 0 <= i <= x ) and ( 0 <= j <= y) This is the code if we dont use list comprehensions in Python.

python x = int ( raw_input()) y = int ( raw_input()) n = int ( raw_input()) ar = [] p = 0 for i in range ( x + 1 ) : for j in range( y + 1): if i+j != n: ar.append([]) ar[p] = [ i , j ] p+=1 print ar 
Other smaller codes may also exist, but using list comprehensions is always a good option. Code using list comprehensions:

python x = int ( raw_input()) y = int ( raw_input()) n = int ( raw_input()) print [ [ i, j] for i in range( x + 1) for j in range( y + 1) if ( ( i + j ) != n )]

Sample Input 1

2
2
2
2

Sample Output 1

[[0, 0, 0], [0, 0, 1], [0, 1, 0], [0, 1, 2], [0, 2, 1], [0, 2, 2], [1, 0, 0], [1, 0, 2], [1, 1, 1],

・ソースコード

if __name__ == '__main__':
    x = int(input())
    y = int(input())
    z = int(input())
    n = int(input())
print ([[i,j,k] for i in range (x+1) for j in range (y+1) for k in range (z+1)if ((i+j+k)!=n) ])

・コメント

print関数の中にforを入れ込んでいる。 さらにその中にif文が含まれているところが少し難解。慣れが必要。 

・URL

https://www.hackerrank.com/challenges/list-comprehensions/problem