std::string::find_last_of in C++ with Examples

The std::string::find_last_of is a string class member function which is used to find the index of last occurrence of any characters in a string. If the character is present in the string then it returns the index of the last occurrence of that character in the string else it returns string::npos.
Header File:

#include < string >

Template Class 

template < class T >
size_type
    find_last_of(const T& t, 
                 size_type pos = npos ) const noexcept();

Syntax 1:

find_last_of(char ch)

Parameters: This function takes a given character and returns the position of the last occurrence of that character.
Below is the program to illustrate string::find_last_of():

CPP

// C++ program to illustrate string::find_last_of
#include <cstddef>
#include <iostream>
#include <string>
using namespace std;

// Driver Code
int main()
{

    // Given String
    string str("Welcome to GeeksforGeeks!");

    // Character to be found
    char ch = 'e';

    // To store the index of last
    // character found
    size_t found;

    // Function to find the last
    // character ch in str
    found = str.find_last_of(ch);

    // If string doesn't have
    // character ch present in it
    if (found == string::npos) {
        cout << "Character " << ch
             << " is not present in"
             << " the given string.";
    }

    // Else print the last position
    // of the character
    else {
        cout << "Character " << ch
             << " is found at index: "
             << found << endl;
    }
}

Output:

Character e is found at index: 21

Time Complexity: O(N), here N is the length of the given string and time complexity string::find_last_of() is O(N).
Auxiliary Space: O(1), since we not used any extra space.

Syntax 2:

find_last_of(char ch, size_t position)

Parameters: This function takes a given character and an index till where the search is to be performed. It returns the position of the last occurrence of that character.
Below is the program to illustrate string::find_last_of():

CPP

// C++ program to illustrate string::find_last_of
#include <cstddef>
#include <iostream>
#include <string>
using namespace std;

// Driver Code
int main()
{

    // Given String
    string str("Welcome to GeeksforGeeks!");

    // Character to be found
    char ch = 'e';

    // To store the index of last
    // character found
    size_t found;

    // Position till search is performed
    int pos = 10;

    // Function to find the last
    // character ch in str[0, pos]
    found = str.find_last_of(ch, pos);

    // If string doesn't have
    // character ch present in it
    if (found == string::npos) {
        cout << "Character " << ch
             << " is not present in"
             << " the given string.";
    }

    // Else print the last position
    // of the character
    else {
        cout << "Character " << ch
             << " is found at index: "
             << found << endl;
    }
}

Output:

Character e is found at index: 6

Time Complexity: O(N), where N is the length of the given string.
Auxiliary Space: O(1).

References: http://www.cplusplus.com/reference/string/string/find_last_of/