C++: Find matching characters in character array

Question

How do I implement a c++ script to search a group of characters from an character array.The search characters are not case sensitive.For an example, I key in "aBc" and the character array has "abcdef" and it is a hit and shows the found.

This is my script,don't know what is wrong.

#include <iostream>
#include <cstdlib>
#include <cstring>

using namespace std;

int main()
{
  char charArr1[]="abcdefghi";
  char inputArr[20];

  cin>>inputArr;
  charArr1.find("abc");
}

I recevied this error. request for member 'find' in 'charArr1', which is of non-class type 'char [10]

Is there any reason why you don't use std::string? This would be a lot easier. — Shafik Yaghmour
– Shafik Yaghmour, Commented Jul 19, 2013 at 14:40

Community · Accepted Answer · 2017-05-23 11:49:13Z

3

copy your inputs and convert them to lower case (see How to convert std::string to lower case?)
perform usual search (http://www.cplusplus.com/reference/string/string/find/)

edited May 23, 2017 at 11:49

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answered Jul 19, 2013 at 14:09

Yulia V

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2 Comments

nubbear Over a year ago

Sorry for the spam, I am new here. Thanks for the reply!

James Kanze Over a year ago

The answer in the link you post is incorrect, and invokes undefined behavior (at least on many platforms). You cannot call ::tolower with a char.

James Kanze · Accepted Answer · 2013-07-19 14:41:53Z

The easiest solution is to convert the input to lower case, and use std::search:

struct ToLower
{
    bool operator()( char ch ) const
    {
        return ::tolower( static_cast<unsigned char>( ch ) );
    }
};

std::string reference( "abcdefghi" );
std::string toSearch;
std::cin >> toSearch;
std::transform( toSearch.begin(), toSearch.end(), toSearch.begin(), ToLower() );
std::string::iterator results
    = std::search( reference.begin(), reference.end(),
                   toSearch.begin(), toSearch.end() );
if ( results != reference.end() ) {
    //  found
} else {
    //  not found
}

The ToLower class should be in your toolkit; if you do any text processing, you'll use it a lot. You'll notice the type conversion; this is necessary to avoid undefined behavior due to the somewhat special interface of ::tolower. (Depending on the type of text processing you do, you may want to change it to use the ctype facet in std::locale. You'd also avoid the funny cast, but the class itself will have to carry some excess bagage to keep a pointer to the facet, and to keep it alive.)

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