- Practice
- Python
- Basic Data Types
- List Comprehensions
List Comprehensions
List Comprehensions
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], [1, 1, 2], [1, 2, 0], [1, 2, 1], [1, 2, 2], [2, 0, 1], [2, 0, 2], [2, 1, 0], [2, 1, 1], [2, 1, 2], [2, 2, 0], [2, 2, 1], [2, 2, 2]]