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Comparing two string using comparison operators in C++ STL
C++ STL | string comparison: In this article, we are going to see how we can use comparison operators to compare two strings in C++?
Submitted by Radib Kar, on February 27, 2019
String as datatype
In C, we know string basically a character array terminated by \0. Thus to operate with the string we define character array. But in C++, the standard library gives us the facility to use the string as a basic data type like an integer. Like integer comparisons, we can do the same for strings too.
Example:
Like we define and declare,
int i=5, j=7;
Same way, we can do for a string like,
string s1="Include", s2="Help";
Like integers (i==j) , (i>j), (i<j)
We can also do the same like
if(s1==s2)
cout << 'They are same\n";
else if(s1>s2)
cout<<s1<<" is greater\n";
else
cout<<s2<< "s2 is greater\n";
Remember, a string variable (literal) need to be defined under "". 'a' is a character whereas "a" is a string.
How comparison between two string works?
'==' operator
Two strings need to be lexicographically same to return true which checking for == operator. "Include" and "Include" is the same. But, "INCLUDE" and "Include" is not same, i.e., case matters.
'>' , '<' operator
This two operator checks which string is greater(smaller) lexicographically. The checking starts from the initial character & checking is done as per ascii value. The checking continues until it faces the same character from both strings. Like,
"Include" > "Help" as 'I' > 'H'
"Include" < "India" as 'c' < 'd'
Header file needed:
#include <string>
Or
#include <bits/stdc++.h>
C++ program to compare two strings using comparison operator (==)
#include <bits/stdc++.h>
using namespace std;
void compare(string a, string b){
if(a==b)
cout<<"strings are equal\n";
else if(a<b)
cout<<b<<" is lexicografically greater\n";
else
cout<<a<<" is lexicografically greater\n";
}
int main(){
string s1,s2;
cout<<"enter string1\n";
cin>>s1;
cout<<"enter string2\n";
cin>>s2;
compare(s1,s2); //user-defined function to comapre
return 0;
}
Output
First run:
enter string1
Include
enter string2
Help
Include is lexicografically greater
Second run:
enter string1
Include
enter string2
India
India is lexicografically greater