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Asked By | praveenyadav1602 |
how to subtract list form list
var x = [1,2,3,4,5,6,7,8,9,0]
var y = [1,3,5,7,9]
var r = (y - x) # (should return [2,4,6,8,0])
also tried:
x = list(set(x)-set(y))
how to get desire output?
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Reply From: | supper_raptor |
You can make a function for this.
func subtractArr(a : Array, b : Array) -> Array:
var final_arr = Array()
a.sort()
b.sort()
var b_index = 0
var b_size = b.size()
for i in a:
if b_index >= b_size or i != b[b_index]:
final_arr.append(i)
if i >= b[b_index]:
b_index += 1
return final_arr
Usage example
var x = [1,2,3,4,5,6,7,8,9,0]
var y = [1,3,5,7,9]
var r = subtractArr(x,y) # (will return [2,4,6,8,0])
and how to print r
i tried:
func subtractArr(a : Array, b : Array) -> Array:
var final_arr = Array()
a.sort()
b.sort()
var b_index = 0
var b_size = b.size()
for i in a:
if b_index >= b_size or i != b[b_index]:
final_arr.append(i)
if i >= b[b_index]:
b_index += 1
return final_arr
var x = [1,2,3,4,5,6,7,8,9,0]
var y = [1,3,5,7,9]
var r = subtractArr(x,y)
func prin():
print (r)
praveenyadav1602 | 2020-04-09 07:17
Why not just
print(r)
Instead of declaring a whole function for this? However, if you do so, you also have to call your declared function to execute it:
func prin():
print(r)
prin() # Call the function to execute it
Blackthorn | 2020-04-09 07:34
You can make a function to print and final code will be -
func printArr(arr : Array):
for i in arr:
print(i)
func subtractArr(a : Array, b : Array) -> Array:
var final_arr = Array()
a.sort()
b.sort()
var b_index = 0
var b_size = b.size()
for i in a:
if b_index >= b_size or i != b[b_index]:
final_arr.append(i)
if i >= b[b_index]:
b_index += 1
return final_arr
var x = [1,2,3,4,5,6,7,8,9,0]
var y = [1,3,5,7,9]
var r = subtractArr(x,y)
printArr(r)
supper_raptor | 2020-04-09 07:36
@blackthorn
var y = [1,3,5,7,9]
var r = subtractArr(x,y)
print (r)
not working returened error unexpected token: Build-in Func:
func prin():
print(r)
prin()
above also not working error:unexpected token: Identifier:prin
@supper_raptor whole code snipt copy paste but not working error:unexpected token: Identifier:prin
checked indent level, but not working
praveenyadav1602 | 2020-04-09 08:01
Bro printArr and subtractArr are functions
printArr prints array and substractArray substracts array/list
You need to call substractArray then printArr
func printArr(arr : Array):
for i in arr:
print(i)
func subtractArr(a : Array, b : Array) -> Array:
var final_arr = Array()
a.sort()
b.sort()
var b_index = 0
var b_size = b.size()
for i in a:
if b_index >= b_size or i != b[b_index]:
final_arr.append(i)
if i >= b[b_index]:
b_index += 1
return final_arr
Both are functions you need to call them to use.
for example if you need to use them in ready() ,then the code is
func _ready():
var x = [1,2,3,4,5,6,7,8,9,0]
var y = [1,3,5,7,9]
var r = subtractArr(x,y) # (will return [2,4,6,8,0])
printArr(r)
supper_raptor | 2020-04-09 10:40
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Reply From: | Poobslag |
Here’s an alternative subtract function, based on Apache Commons Collections:
static func subtract(a: Array, b: Array) -> Array:
var result := []
var bag := {}
for item in b:
if not bag.has(item):
bag[item] = 0
bag[item] += 1
for item in a:
if bag.has(item):
bag[item] -= 1
if bag[item] == 0:
bag.erase(item)
else:
result.append(item)
return result
supper_raptor’s solution fails for some edge cases, such as subtract([1, 1, 1, 1, 1], [1, 1, 1]) which actually throws an error. This implementation returns the correct result.
There is even simpler solution for this:
func subtract_arrays(a: Array, b: Array) -> Array:
var result = a.duplicate()
for item in b:
result.erase(item)
return result
Function erase removes the first occurrence of a value from the array. If the value does not exist in the array, nothing happens. That means you don’t have to check if the value is in the array.
You have to duplicate the a array, otherwise it will get modified.