C Program To Replace First Occurrence of a Character in a String

In this tutorial, i am going to show you how to replace first occurrence of a character in a string with help of for loop, while loop, recursion and functions in c programs.

All C Programs and Algorithm To Replace First Occurrence of a Character in a String

• Algorithm To Replace First Occurrence of a Character in a String
• C Program To Replace First Occurrence of a Character in a String using For Loop
• C Program To Replace First Occurrence of a Character in a String using While Loop
• C Program To Replace First Occurrence of a Character in a String using Function
• C Program To Replace First Occurrence of a Character in a String using Recursion

Algorithm To Replace First Occurrence of a Character in a String

Follow the below given algorithm to write a program to replace first occurrence of a character with in a string; as follows:

1. Input string from user, store it in some variable.
2. Input character to replace and character new character from user, store it in some variables.
3. Iterate a loop from start of string str to end.
4. Inside the loop, swap old character with new character and terminate the loop.
5. Print result.

C Program To Replace First Occurrence of a Character in a String using For Loop

#include <stdio.h>
#include <string.h>
 
int main()
{
    char s[1000],c1,c2;  
    int  i;
 
    printf("Enter  the string : ");
    gets(s);
    
	printf("Enter a character replace: ");
    c1=getchar();
    getchar();
    printf("\nEnter character to replace  %c with: ",c1);
    c2=getchar();
    printf("\n before replace:%s",s);
 
    for(i=0;s[i];i++) 
	{  
		if(s[i]==c1)
		{
		   s[i]=c2;
		   break;
	    }
	}
	   
    printf("\nafter replace:%s",s);
 	 
     
    return 0;
}

The result of the above c program; as follows:

Enter  the string : hello
Enter a character replace: h
Enter character to replace  h with: w
before replace:hello
after replace:wello

C Program To Replace First Occurrence of a Character in a String using While Loop

/* C Program to Replace First Occurrence of a Character in a String */
 
#include <stdio.h>
#include <string.h>
 
int main()
{
  	char str[100], ch, Newch;
  	int i = 0;
 
  	printf("\n Please Enter any String :  ");
  	gets(str);
  	
  	printf("Enter a character replace: ");
  	
  	scanf("%c", &ch);
  	
  	getchar();
  	
  	printf("\nEnter character to replace  %c with: ",ch);
  	scanf("%c", &Newch);
  	
  	while(i <= strlen(str))
  	{
  		if(str[i] == ch)  
		{
  			str[i] = Newch;
  			break;
 		}
 		i++;
	}
	printf("\n The Final String after Replacing First occurrence of '%c' with '%c' = %s ", ch, Newch, str);
	
  	return 0;
}

The result of the above c program; as follows:

Please Enter any String :  hello
Enter a character replace: h
Enter character to replace  h with: w
The Final String after Replacing First occurrence of 'h' with 'w' = wello 

C Program To Replace First Occurrence of a Character in a String using Function

/* C Program to Replace First Occurrence of a Character in a String */
 
#include <stdio.h>
#include <string.h>
void Replace_FirstOccurrence(char *str, char ch, char Newch);
 
int main()
{
  	char str[100], ch, Newch;
  	int 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);
  	
  	Replace_FirstOccurrence(str, ch, Newch);
  	
  	printf("\n The Final String after Replacing First occurrence of '%c' with '%c' = %s ", ch, Newch, str);
	
  	return 0;
}
void Replace_FirstOccurrence(char *str, char ch, char Newch)
{
	int i;
	for(i = 0; str[i] != '\0'; i++)
	{
		if(str[i] == ch)
		{
			str[i] = Newch;
  			break;
		}  
	}
}

The result of the above c program; as follows:

Please Enter any String :  fans
Please Enter the Character that you want to Replace :  f
Please Enter the New Character :  v
The Final String after Replacing First occurrence of 'f' with 'v' = vans 

C Program To Replace First Occurrence of a Character in a String using Recursion

 #include <stdio.h>
#include <string.h>
 
void replacechar(char *s,char c1,char c2)
{
	static int i=0;
 
    
 
    if(s[i]==c1)
    {
     	s[i]=c2;
     	return;
    }
    i++;
    replacechar(s,c1,c2);
 
	 
	     
       
	   
  	 
}
 
 
int main()
{
 
    char s[1000],c1,c2;  
  
    printf("Enter  the string : ");
    gets(s);
    
	printf("Enter a character replace: ");
    c1=getchar();
    getchar();
    printf("\nEnter character to replace  %c with: ",c1);
    c2=getchar();
    printf("\n before replace:%s",s);
 
    replacechar(s,c1,c2);
	   
    printf("\nafter replace:%s",s);
 	 
     
    return 0;
 
     
     
} 

The result of the above c program; as follows:

Enter  the string : sony
Enter a character replace: s
Enter character to replace  s with: w
before replace:sony
after replace:wony

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