Question

How to compare two strings ignoring the case in C++

Answer 1

#include <iostream>
#include <cstring>
 
int main() {
    std::string s1 = "C++ PROGRAMMING";
    std::string s2 = "c++ programming";
     
    if (strcasecmp(s1.c_str(), s2.c_str()) == 0) {
        std::cout << "s1 == s2";
    } else {
        std::cout << "s1 != s2";
    }
}

 
 
/*
run:
 
s1 == s2
 
*/

 

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Answer 2

#include <iostream>
#include <cstring>
 
int main() {
    std::string s1 = "C++ PROGRAMMING";
    std::string s2 = "c++ programming";
     
    if (strncasecmp(s1.c_str(), s2.c_str(), s1.size()) == 0) {
        std::cout << "s1 == s2";
    } else {
        std::cout << "s1 != s2";
    }
}

 
 
/*
run:
 
s1 == s2
 
*/

 

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Answer 3

#include <iostream>
#include <algorithm>
 
std::string toLower(std::string s) {
    transform(s.begin(), s.end(), s.begin(),
               [](unsigned char ch){ return std::tolower(ch); });
    return s;
}
 
int main() {
    std::string s1 = "C++ PROGRAMMING";
    std::string s2 = "c++ programming";
     
     if (toLower(s1) == toLower(s2)) {
        std::cout << "s1 == s2";
    } else {
        std::cout << "s1 != s2";
    }
}

 
 
/*
run:
 
s1 == s2
 
*/

 

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