Given a C/C++ program, remove comments from it.
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The idea is to maintain two flag variables, one to indicate that a single line comment is started, another to indicate that a multiline comment is started. When a flag is set, we look for the end of comment and ignore all characters between start and end.
Following is C++ implementation of above idea.
C++
// C++ program to remove comments from a C/C++ program #include <iostream> using namespace std;
string removeComments(string prgm) { int n = prgm.length();
string res;
// Flags to indicate that single line and multiple line comments
// have started or not.
bool s_cmt = false ;
bool m_cmt = false ;
// Traverse the given program
for ( int i=0; i<n; i++)
{
// If single line comment flag is on, then check for end of it
if (s_cmt == true && prgm[i] == '\n' )
s_cmt = false ;
// If multiple line comment is on, then check for end of it
else if (m_cmt == true && prgm[i] == '*' && prgm[i+1] == '/' )
m_cmt = false , i++;
// If this character is in a comment, ignore it
else if (s_cmt || m_cmt)
continue ;
// Check for beginning of comments and set the appropriate flags
else if (prgm[i] == '/' && prgm[i+1] == '/' )
s_cmt = true , i++;
else if (prgm[i] == '/' && prgm[i+1] == '*' )
m_cmt = true , i++;
// If current character is a non-comment character, append it to res
else res += prgm[i];
}
return res;
} // Driver program to test above functions int main()
{ string prgm = " /* Test program */ \n"
" int main() \n"
" { \n"
" // variable declaration \n"
" int a, b, c; \n"
" /* This is a test \n"
" multiline \n"
" comment for \n"
" testing */ \n"
" a = b + c; \n"
" } \n" ;
cout << "Given Program \n" ;
cout << prgm << endl;
cout << " Modified Program " ;
cout << removeComments(prgm);
return 0;
} |
Output
Given Program /* Test program */ int main() { // variable declaration int a, b, c; /* This is a test multiline comment for testing */ a = b + c; } Modified Program int main() { int a, b, c; a = b + c; }
Time Complexity :O(N), where N is length of string.
Space Complexity: O(1), since no extra space used.