String compare in C

Using compare()

C++ standard library has an inbuilt function std::string::compare() to string compare in C character by character. It returns the following three types of values:

0, If both the strings are equal.

>0, If the first string is lexicographically greater than the second.

<0, If the second string is lexicographically greater than the first.

Implementation

#include <bits/stdc++.h>
using namespace std;

// C program to compare the two strings
int main(){
    string a = "abzc";
    string b = "abcz";
    cout<<a<<' '<<b<<' '<<a.compare(b)<<endl;

    a = "abcz";
    b = "abzc";
    cout<<a<<' '<<b<<' '<<a.compare(b)<<endl;

    a = "abcd";
    b = "abcd";
    cout<<a<<' '<<b<<' '<<a.compare(b)<<endl;
}

Output

abzc abcz 1
abcz abzc -1
abcd abcd 0

Using C strcmp()

C strcmp() is a function to string compare in C. Its output also follows the same rules as compare().

Implementation

#include <bits/stdc++.h>
using namespace std;

// Compare two strings using strcmp()
int main(){
    char a[] = "abzc";
    char b[] = "abcz";
    cout<<strcmp(a,b)<<endl;
}

Have a look also on strcat() function in C and Short int in C Programming

Must Read Passing Arrays to Function in C

Using strncmp()

std::strncmp() takes three arguments - String A, String B, Integer N. It is used to string compare in C for maximum N characters. It first compares the first characters of both the strings. If the characters are the same, it compares the second character and so on. If at any position, the characters mismatch, it returns the answer accordingly. This process stops if either the null-character (\0) is encountered in any string or it has made N comparisons.

Implementation

#include <bits/stdc++.h>
using namespace std;

// String compare in C using strncmp()
int main(){
    char a[] = "abzc";
    char b[] = "abcz";
    cout<<strncmp(a,b,3)<<endl;
}

For better understanding try it on online C compiler.

Time Complexity

To string compare in C, we need to check the first character where these strings mismatch. To do these, we iterate over the minimum length of both strings. Therefore the time complexity to string compare in C is O(min(length(A), length(B))).

Space Complexity

For comparing two strings, we just need to use some variables. Therefore, the space complexity is O(1).

Must Read Decision Making in C

FAQs

1. What is the return value of C strcmp()?
   C Strcmp() is an inbuilt function that compares two strings (character arrays) in C/C++. It returns 0 if both the strings are equal, >0 if the ASCII value of the first character where both the strings mismatch is greater in the first string, and <0 if it is greater in the second string.
2. How does C strcmp() function work?
   Strcmp() function is used to string compare in C two strings character by character. If the first character in both the strings is the same, then it compares the second character and so on until a mismatch is found.
3. What is the difference between C strcmp() and strncmp()?
   Strcmp() takes two strings as input and compares them by character until a mismatch is found. Strncmp() also does the same thing but only for the first ‘N’ characters, where ‘N’ is the third argument of the function.

Key Takeaways

In this article, we have extensively discussed different ways to string compare in C and their implementation in C++. We hope that this blog has helped you enhance your knowledge on comparing two strings in C++ and if you would like to learn more, check out our articles on Coding Ninjas Studio. Do upvote our blog to help other ninjas grow. Happy Coding!”