C Program to Replace Last Occurrence of a Character in a String

Write a C Program to Replace Last Occurrence of a Character in a String with example.

C Program to Replace Last Occurrence of a Character in a String Example 1

This C program allows the user to enter a string (or character array), and a character value. Next, it will find and replace last occurrence of a character inside a string.

/* C Program to Replace Last Occurrence of a Character in a String */
 
#include <stdio.h>
#include <string.h>
 
int main()
{
  	char str[100], ch, Newch;
  	int i, index;
  	index = -1;
 
  	printf("\n Please Enter any String :  ");
  	gets(str);
  	
  	printf("\n Please Enter the Character that you want to Replace :  ");
  	scanf("%c", &ch);
  	
  	getchar();
  	
  	printf("\n Please Enter the New Character :  ");
  	scanf("%c", &Newch);
  	
  	for(i = 0; str[i] != '\0'; i++)
  	{
  		if(str[i] == ch)  
		{
  			index = i;
 		}
	}
	
	if(index != -1)
  	{
  		str[index] = Newch;
	}

	printf("\n The Final String after Replacing Last occurrence of '%c' with '%c' = %s ", ch, Newch, str);
	
  	return 0;
}

First, we used For Loop to iterate every character in a C Programming String.

for(i = 0; i <= strlen(str); i++)
{
	if(str[i] == ch)  
	{
		index = i;  	
	}
}

Next, we used the If Statement to check the index value is not equal to -1. If it is True then execute str[index] = Newch;
str[] = Hello
ch = l
Newch = @
Index = -1

For Loop First Iteration: for(i = 0; i <= strlen(str); i++)
The condition is True because i <= 5.

Within the While Loop, we used If statement to check whether the str[0] is equal to a user-specified character or not

if(str[i] == ch) => if(H == l) – condition is false. So, i value will be incremented, and Index value is still -1.

Second Iteration: for(i = 1; 1 <= 5; 1++)
if(str[i] == ch) => if(e == l) – condition is false. So, i will increment, and Index value is still -1.

Third Iteration: for(i = 2; 2 <= 5; 2++)
if(str[i] == ch) => if(l == l) – condition is True
Index  = i
index  = 2

Third Iteration: for(i = 3; 3 <= 5; 3++)
if(str[i] == ch) => if(l == l) – condition is True
index  = i = 3

Do the same for remaining iterations.

Next, we used the If Statement to check the index value is equal to -1. Here, the condition is True so,
str[index]  =Newch
str[3] = @

At last, we used the printf statement to print the final string

printf("\n The Last Occurrence of the Search Element '%c' is at Position %d ", ch, i + 1);

C Program to Replace Last Occurrence of a Character in a String Example 2

This program to replace last character occurrence is the same as above. Here, we just replaced the For Loop with While Loop.

/* C Program to Replace Last Occurrence of a Character in a String */

#include <stdio.h>
#include <string.h> 

int main()
{
  	char str[100], ch, Newch;
  	int i, index;
  	index = -1;
  	i = 0;
 
  	printf("\n Please Enter any String :  ");
  	gets(str);
  	
  	printf("\n Please Enter the Character that you want to Replace :  ");
  	scanf("%c", &ch);  	
  	getchar();
  	
  	printf("\n Please Enter the New Character :  ");
  	scanf("%c", &Newch);
  	
  	while(i <= strlen(str))
  	{
  		if(str[i] == ch)  
		{
  			index = i;
 		}
 		i++;
	}
	
	if(index != -1)
  	{
  		str[index] = Newch;
	}

	printf("\n The Final String after Replacing Last occurrence of '%c' with '%c' = %s ", ch, Newch, str);
	
  	return 0;
}

 Please Enter any String :  tutorial gateway

 Please Enter the Character that you want to Replace :  t

 Please Enter the New Character :  #

 The Final String after Replacing Last occurrence of 't' with '#' = tutorial ga#eway

C Program to Replace Last Occurrence of a Character in a String Example 3

This program to replace the last character occurrence is the same as the first example. Still, this time, we applied the Functions concept to separate the logic.

/* C Program to Replace Last Occurrence of a Character in a String */
 
#include <stdio.h>
#include <string.h>

void Replace_LastOccurrence(char *str, char ch, char Newch);
 
int main()
{
  	char str[100], ch, Newch;
  	int i, index;
  	index = -1;
 
  	printf("\n Please Enter any String :  ");
  	gets(str);
  	
  	printf("\n Please Enter the Character that you want to Replace :  ");
  	scanf("%c", &ch);
  	
  	getchar();
  	
  	printf("\n Please Enter the New Character :  ");
  	scanf("%c", &Newch);
  	
  	Replace_LastOccurrence(str, ch, Newch);

	printf("\n The Final String after Replacing Last occurrence of '%c' with '%c' = %s ", ch, Newch, str);
	
  	return 0;
}

void Replace_LastOccurrence(char *str, char ch, char Newch)
{
	int i, index;
  	index = -1;

	for(i = 0; str[i] != '\0'; i++)
	{
		if(str[i] == ch)
		{
			index = i;
		}  
	}
	
	if(index != -1)
  	{
  		str[index] = Newch;
	}
}

 Please Enter any String :  c programming

 Please Enter the Character that you want to Replace :  m

 Please Enter the New Character :  $

 The Final String after Replacing Last occurrence of 'm' with '$' = c program$ing