Quick way to check if all the characters of a string are same

Given a string, check if all the characters of the string are same or not.

Examples:

Input : s = "geeks"
Output : No

Input : s = "gggg" 
Output : Yes

Simple Way


To find whether string has all the same characters. Traverse the whole string from index 1 and check whether that character matches with first character of string or not. If yes, than match until string size. If no, than break the loop.

// C++ program to find whether the string
// has all same characters or not.
#include <iostream>
using namespace std;

bool allCharactersSame(string s)
{
    int n = s.length();
    for (int i = 1; i < n; i++)
        if (s[i] != s[0])
            return false;

    return true;
}

// Driver code
int main()
{
    string s = "aaa";
    if (allCharactersSame(s)
        cout << "Yes\n";
    else
        cout << "No\n";

    return 0;
}

Output:

Yes

Quick Way (Not time complexity wise, but in terms of number of lines of code)


The idea is to use find_first_not_of() in C++ STL.

find_first_not_of() finds and returns position of first character that does not match a specified character (or any of the specified characters in case of a string).

// A quick C++ program to find whether the
// string has all same characters or not.
#include <iostream>
using namespace std;

bool allCharactersSame(string s)
{
    return (s.find_first_not_of(s[0]) == string::npos);
}

// Driver code
int main()
{
    string s = "aaa";
    if (allCharactersSame(s))
        cout << "Yes\n";
    else
        cout << "No\n";

    return 0;
}

Output:

yes

This article is contributed by Jatin Goyal. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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