Why does x print as 0 for this code forces problem?

Question

n = int(input())
x = 0
operations = ["++", "--"]
lst = []
for i in range(0, n):
    statements = input().split()
    lst.append(statements)
for statement in lst:
    if operations[0] in lst:
        x += 1
    if operations[1] in lst:
        x -= 1
print(x)

CodeForces Link

How do I make it so if the users input contains "++" it adds 1 to x and if it contains "--" it will subtract 1 from x?

Answer 1

if operations[0] in lst: if operations[1] in lst:都将返回 True，因此您在每个循环中加 1 和减 1。

Answer 2

Your second for loop isn't doing what you're looking for. You are checking to see if '++' is in the lst and checking the same for '--' .

You are already looping over the statement in lst , so there is no reason to do that check. Instead you can do:

for statement in lst:
    if statement == operations[0]:
        x += 1
    elif statement == operations[1]:
        x -= 1

Answer 3

For the if statements do:

if statement == operations[0]:
  x += 1
#And so on...

Your if statements are checking if there is a ++ or -- in the whole list, not each statement.