Remove part of the string between the comments along with the comments

Here’s a string. I want to remove a C-style comments with the comments itself. Without using regex

a = "word234 /*12aaa12*/"

I want the output to be just:

word234

Answer

Here is a simple algorithm that keep the state over 2 characters and uses a flag to keep or not the characters.

a = "word234 /*12aaa12*/ word123 /*xx*xx*/ end"

out = []
add = True
prev = None
for c in a:
    if c == '*' and prev == '/':
        if add:
            del out[-1]
        add = False
    if c == '/' and prev == '*':
        add = True
        prev = c
        continue
    prev = c
    if add:
        out.append(c)
s2 = ''.join(out)
print(s2)

Output:

word234  word123  end

If you want to handle nested comments (not sure if this exists, but this is fun to do), the algorithm is easy to modify to use a flag that counts the depth level:

a = "word234 /*12aaa12*/ word123 /*xx/*yy*/xx*/ end"

out = []
lvl = 0
prev = None
for c in a:
    if c == '*' and prev == '/':
        if lvl == 0:
            del out[-1]
        lvl -= 1
    if c == '/' and prev == '*':
        lvl += 1
        prev = c
        continue
    prev = c
    if lvl == 0:
        out.append(c)
s2 = ''.join(out)
print(s2)