Check if Char Array contains a string in C++

This tutorial will discuss about unique ways to check if char array contains a string in C++.

Table Of Contents

Technique 1: Check if a char array contains a substring

The strstr() function takes two strings as arguments i.e.

strstr(const char* source, const char* target)

It looks for the first occurrence of target string in the source string, and returns the pointer to the first character of the matched string in the source string. If the target string does not exists in the source string then it returns NULL.

We can use this strstr() function to check if a char array contains a string or not. We have created a function for it,

// Check if a char array contains a substring
bool contains(const char * mainStr, const char * subString)
{
    bool result = false;

    // Get the pointer to first occurrence of 
    // string "subStr" in the "mainStr" String 
    const char * ptr = strstr(mainStr, subString) ;

    // If substring does not exits in the main string,
    // then ptr will be NULL
    if (ptr != NULL)
    {
        result = true;
    }
    return result;
}

We can use this function to check if the char array contains the given substring or not.

Let’s see the complete example,

#include <iostream>
#include <string.h>

// Check if a char array contains a substring
bool contains(const char * mainStr, const char * subString)
{
    bool result = false;

    // Get the pointer to first occurrence of
    // string "subStr" in the "mainStr" String
    const char * ptr = strstr(mainStr, subString) ;

    // If substring does not exits in the main string,
    // then ptr will be NULL
    if (ptr != NULL)
    {
        result = true;
    }
    return result;
}

int main()
{
    char mainStr[50] = "This is a sample text";
    char subString[50] = "sample";

    // Check if Char Array contains a string
    if( contains(mainStr, subString) )
    {
        std::cout<<"Char Array contains the string \n";
    }
    else
    {
        std::cout<<"Char Array does not contains the string \n";
    }
    return 0;
}

Output :

Char Array contains the string

Technique 2: Check if a char array contains a substring

We can cast the char array to a std::string object, and then use the string::find() function to get the index position of first occurrence of another substring in the string. If given substring does not exists in the string, the the ‘find()’ function will return std::string::npos.

We have created a separate function contains() for this,

// Check if a char array contains a substring
bool contains(
        const char * mainStr,
        const char * subString)
{
    // Convert char array to string
    std::string strObj(mainStr) ;

    // Get the index position of substring in the string
    auto pos = strObj.find(subString) ;

    return pos != std::string::npos;
}

We can use this function to check if the char array contains the given substring or not.

Let’s see the complete example,

#include <iostream>
#include <string>

// Check if a char array contains a substring
bool contains(
        const char * mainStr,
        const char * subString)
{
    // Convert char array to string
    std::string strObj(mainStr) ;

    // Get the index position of substring in the string
    auto pos = strObj.find(subString) ;

    return pos != std::string::npos;
}

int main()
{
    char mainStr[50] = "This is a sample text";
    char subString[50] = "sample";

    // Check if Char Array contains a string
    if(contains(mainStr, subString) )
    {
        std::cout<<"Char Array contains the string \n";
    }
    else
    {
        std::cout<<"Char Array does not contains the string \n";
    }

    return 0;
}

Output :

Char Array contains the string

Summary

Today we learned about several ways to check if char array contains a string in C++. Thanks.