C Programming Code Examples
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program to replace first occurrence of a character in a string
/* program to replace first occurrence of a character in a string
Write a C program to replace first occurrence of a character with another character in a string. How to replace first occurrence of a character with another character in a string using loop in C programming. Logic to replace first occurrence of a character in given string.
Logic to replace first occurrence of a character
Input string from user, store it in some variable say str.
Input character to replace and character new character from user, store it in some variable say oldChar and newChar.
Run a loop from start of string str to end. The loop structure should loop like while(str[j]!='\0')
Inside the loop check if(str[j] == oldChar). Then, swap old character with new character i.e. str[j] = newChar and terminate the loop.
C program to replace first occurrence of a character with another in a string */
#include <stdio.h>
#define maxsize 100 // Maximum string size
/* Function declaration */
void replaceFirst(char * str, char oldChar, char newChar);
int main()
{
char str[maxsize], oldChar, newChar;
printf("Enter any string: ");
gets(str);
printf("Enter character to replace: ");
oldChar = getchar();
// Used to skip extra ENTER character
getchar();
printf("Enter character to replace '%c' with: ", oldChar);
newChar = getchar();
printf("\nString before replacing: %s\n", str);
replaceFirst(str, oldChar, newChar);
printf("String after replacing first '%c' with '%c' : %s", oldChar, newChar, str);
return 0;
}
/* Replace first occurrence of a character with another in given string. */
void replaceFirst(char * str, char oldChar, char newChar)
{
int j=0;
/* Run till end of string */
while(str[j] != '\0')
{
/* If an occurrence of character is found */
if(str[j] == oldChar)
{
str[j] = newChar;
break;
}
j++;
}
}
While loop is also known as a pre-tested loop. In general, a while loop allows a part of the code to be executed multiple times depending upon a given boolean condition. It can be viewed as a repeating if statement. The while loop is mostly used in the case where the number of iterations is not known in advance. The while loop evaluates the test expression inside the parentheses (). If test expression is true, statements inside the body of while loop are executed. Then, test expression is evaluated again. The process goes on until test expression is evaluated to false. If test expression is false, the loop terminates.
Get string from stdin. Reads characters from the standard input (stdin) and stores them as a C string into str until a newline character or the end-of-file is reached. The newline character, if found, is not copied into str. A terminating null character is automatically appended after the characters copied to str. Notice that gets is quite different from fgets: not only gets uses stdin as source, but it does not include the ending newline character in the resulting string and does not allow to specify a maximum size for str (which can lead to buffer overflows).
Writes the C string pointed by format to the standard output (stdout). If format includes format specifiers (subsequences beginning with %), the additional arguments following format are formatted and inserted in the resulting string replacing their respective specifiers. printf format string refers to a control parameter used by a class of functions in the input/output libraries of C programming language. The string is written in a simple template language: characters are usually copied literally into the function's output, but format specifiers, which start with a % character, indicate the location and method to translate a piece of data (such as a number) to characters. "printf" is the name of one of the main C output functions, and stands for "print formatted". printf format strings are complementary to scanf format strings, which provide formatted input (parsing). In both cases these provide simple functionality and fixed format compared to more sophisticated and flexible template engines or parsers,
Get character from stdin. Returns the next character from the standard input (stdin). It is equivalent to calling getc with stdin as argument. A getchar() function is a non-standard function whose meaning is already defined in the stdin.h header file to accept a single input from the user. In other words, it is the C library function that gets a single character (unsigned char) from the stdin. However, the getchar() function is similar to the getc() function, but there is a small difference between the getchar() and getc() function of the C programming language.
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