Find last index of a character in a string

Given a string str and a character x, find last index of x in str.

Examples :

Input : str = "geeks", x = 'e'
Output : 2
Last index of 'e' in "geeks" is: 2 

Input : str = "Hello world!", x = 'o'
Output : 7
Last index of 'o' is: 7

Recommended: Please solve it on PRACTICE first, before moving on to the solution.

Method 1 (Simple : Traverse from left) :
Traverse given string from left to right and keep updating index whenever x matches with current character.

C++

// CPP program to find last index of 
// character x in given string. 
#include <iostream> 
using namespace std; 
  
// Returns last index of x if it is present. 
// Else returns -1. 
int findLastIndex(string& str, char x) 
{ 
    int index = -1; 
    for (int i = 0; i < str.length(); i++) 
        if (str[i] == x) 
            index = i; 
    return index; 
} 
  
// Driver code 
int main() 
{ 
    // String in which char is to be found 
    string str = "geeksforgeeks"; 
  
    // char whose index is to be found 
    char x = 'e'; 
    int index = findLastIndex(str, x); 
    if (index == -1) 
        cout << "Character not found"; 
    else
        cout << "Last index is " << index; 
    return 0; 
} 

Java

// Java program to find last index 
// of character x in given string. 
import java.io.*; 
  
class GFG { 
   
// Returns last index of x if 
// it is present Else returns -1. 
static int findLastIndex(String str, Character x) 
{ 
    int index = -1; 
    for (int i = 0; i < str.length(); i++) 
        if (str.charAt(i) == x) 
            index = i; 
    return index; 
} 
   
// Driver code 
public static void main(String[] args) 
{ 
    // String in which char is to be found 
    String str = "geeksforgeeks"; 
  
    // char whose index is to be found 
    Character x = 'e'; 
  
    int index = findLastIndex(str, x); 
    if (index == -1) 
        System.out.println("Character not found"); 
    else
        System.out.println("Last index is " + index); 
} 
} 
  
/* This code is contributed by Prerna Saini */

Python3

# A Python program to find last 
# index of character x in given 
# string. 
  
# Returns last index of x if it 
# is present. Else returns -1. 
def findLastIndex(str, x): 
    index = -1
    for i in range(0, len(str)): 
        if str[i] == x: 
            index = i 
    return index 
  
# Driver program 
  
# String in which char is to be found 
str = "geeksforgeeks"
  
# char whose index is to be found 
x = 'e'
  
index = findLastIndex(str, x) 
  
if index == -1: 
    print("Character not found") 
else: 
    print('Last index is', index) 
  
# This code is contributed by shrikant13. 

C#

// C# program to find last index 
// of character x in given string. 
using System; 
  
class GFG { 
  
    // Returns last index of x if 
    // it is present Else returns -1. 
    static int findLastIndex(string str, char x) 
    { 
        int index = -1; 
        for (int i = 0; i < str.Length; i++) 
            if (str[i] == x) 
                index = i; 
        return index; 
    } 
      
    // Driver code 
    public static void Main() 
    { 
        // String in which char is to be found 
        string str = "geeksforgeeks"; 
      
        // char whose index is to be found 
        char x = 'e'; 
      
        int index = findLastIndex(str, x); 
        if (index == -1) 
            Console.WriteLine("Character not found"); 
        else
            Console.WriteLine("Last index is " + index); 
    } 
} 
  
/* This code is contributed by vt_m */

PHP

<?php 
// PHP program to find last index of 
// character x in given string. 
  
// Returns last index of  
// x if it is present. 
// Else returns -1. 
function findLastIndex($str, $x) 
{ 
    $index = -1; 
    for ($i = 0; $i < strlen($str); $i++) 
        if ($str[$i] == $x) 
            $index = $i; 
    return $index; 
} 
  
// Driver code 
// String in which  
// char is to be found 
$str = "geeksforgeeks"; 
  
// char whose index 
// is to be found 
$x = 'e'; 
$index = findLastIndex($str, $x); 
if ($index == -1) 
    echo("Character not found"); 
else
    echo("Last index is " . $index); 
  
// This code is contributed by Ajit. 
?> 

Output:

Last index is 10

Time Complexity : Θ(n)

Method 2 (Efficient : Traverse from right) :
In above method 1, we always traverse complete string. In this method, we can avoid complete traversal in all those cases when x is present. The idea is to traverse from right side and stop as soon as we find character.

CPP

// Simple CPP program to find last index of 
// character x in given string. 
#include <iostream> 
using namespace std; 
  
// Returns last index of x if it is present. 
// Else returns -1. 
int findLastIndex(string& str, char x) 
{ 
    // Traverse from right 
    for (int i = str.length() - 1; i >= 0; i--) 
        if (str[i] == x) 
            return i; 
  
    return -1; 
} 
  
// Driver code 
int main() 
{ 
    string str = "geeksforgeeks"; 
    char x = 'e'; 
    int index = findLastIndex(str, x); 
    if (index == -1) 
        cout << "Character not found"; 
    else
        cout << "Last index is " << index; 
    return 0; 
} 

Java

// Java code to find last index 
// character x in given string. 
import java.io.*; 
class GFG { 
   
// Returns last index of x if 
// it is present. Else returns -1. 
static int findLastIndex(String str, Character x) 
{ 
    // Traverse from right 
    for (int i = str.length() - 1; i >= 0; i--) 
        if (str.charAt(i) == x) 
            return i; 
  
    return -1; 
} 
   
// Driver code 
public static void main(String[] args) 
{ 
    String str = "geeksforgeeks"; 
    Character x = 'e'; 
    int index = findLastIndex(str, x); 
    if (index == -1) 
        System.out.println("Character not found"); 
    else
        System.out.println("Last index is " + index); 
} 
} 
// This code is contributed by Prerna Saini 

Python3

# Simple Python3 program to find last 
# index of character x in given string. 
  
# Returns last index of x if it is  
# present. Else returns -1. 
def findLastIndex(str, x): 
  
    # Traverse from right 
    for i in range(len(str) - 1, -1,-1): 
        if (str[i] == x): 
            return i 
  
    return -1
  
# Driver code 
str = "geeksforgeeks"
x = 'e'
index = findLastIndex(str, x) 
  
if (index == -1): 
    print("Character not found") 
else: 
    print("Last index is " ,index) 
  
# This code is contributed by Smitha 

C#

// C# code to find last index 
// character x in given string. 
using System; 
  
class GFG { 
  
    // Returns last index of x if 
    // it is present. Else returns -1. 
    static int findLastIndex(string str, char x) 
    { 
        // Traverse from right 
        for (int i = str.Length - 1; i >= 0; i--) 
            if (str[i] == x) 
                return i; 
      
        return -1; 
    } 
      
    // Driver code 
    public static void Main() 
    { 
        string str = "geeksforgeeks"; 
        char x = 'e'; 
        int index = findLastIndex(str, x); 
        if (index == -1) 
            Console.WriteLine("Character not found"); 
        else
            Console.WriteLine("Last index is " + index); 
    } 
} 
// This code is contributed by vt_m 

PHP

<?php 
// Simple PHP program to find last index  
// of character x in given string. 
  
// Returns last index of x if it  
// is present. Else returns -1. 
function findLastIndex($str, $x) 
{ 
      
    // Traverse from right 
    for ($i = strlen($str) - 1; $i >= 0; $i--) 
        if ($str[$i] == $x) 
            return $i; 
  
    return -1; 
} 
  
// Driver code 
$str = "geeksforgeeks"; 
$x = 'e'; 
$index = findLastIndex($str, $x); 
if ($index == -1) 
    echo("Character not found"); 
else
    echo("Last index is " . $index); 
  
// This code is contributed by Ajit. 
?> 

Output:

Last index is 10

Time Complexity : O(n)

My Personal Notes

Suggest a Topic

Recommended: Please solve it on PRACTICE first, before moving on to the solution.

C++

Java

Python3

C#

PHP

CPP

Java

Python3

C#

PHP

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