”’

def combination(n,k):

combi=[]

def backtrack(start,comb):
    print(comb)
    if len(comb)==k:
        combi.append(comb.copy())
        return 
        
    for i in range(start,n+1):
        # print(i)
        cur=[i]
        backtrack(i+1,comb+cur)
        comb.pop()
        print("comb after",comb)
backtrack(1,[])
return combi

combination(4,3)

”’

I am getting error, IndexError: pop from empty list
When i printed comb to identify error, i am getting this:

1
[]
i is 1
2
[1]
i is 2
3
[1, 2]
i is 3
4
[1, 2, 3]
comb after [1]
i is 4
5
[1, 4]
comb after []
comb after []
i is 3
4
[3]
i is 4
5
[3, 4]
comb after []

Why is my code popping 2 and 3 both when it should only pop 3 after getting [1,2,3].What am i doing wrong?