C program to check if two strings are different by one and only one character
#include<stdio.h> 
#include<string.h> 
//driver function 
int main()
{ 
 int result; 
 char f_string[100],s_string[100]; /* Declaring f_string and s_string as strings*/
 
printf("Enter the first string : \\"); // Taking inputs from user 
 scanf("%s",f_string); 
 printf("Enter the second string : \\"); // 
 scanf("%s",s_string); 
 int l1 = strlen(f_string); // calculating length of strings
 int l2 = strlen(s_string); 
 int difference = 0; // For storing the count difference in strings 
 if(l1==l2) // Checking lengths of string
 {
 for(int i=0;i<l2;i++) 
 {
 if(f_string[i] !=s_string[i]) /*checking each character of f_string with the same character index of s_string*/ 
 difference++; // updating the count difference
 } 
 }
 result=difference;
 if(result==1) // if there is only one character difference
 printf("The two strings are replaced by one character"); 
 else 
 printf("The two strings are not replaced by one character"); 
}
Output
Enter the first string : lake
Enter the second string : bake
The two strings are replaced by one character
Enter the first string : pal
Enter the second string : pale
The two strings are not replaced by one character
Enter the first string : bus
Enter the second string : bit
The two strings are not replaced by one character
Enter the first string : kite
Enter the second string : bit
The two strings are not replaced by one character