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++ 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.
