The input consists of a character we want to check, if it exists in the string. So we agree - it may or may not be faster. If s2 isn't found, it returns a null . Write an efficient function to implement strcpy () function in C. The standard strcpy () function copies a given C-string to another string. . C Language | string.h | strlen() | strcpy() | strcat() | strcmp ... Count Occurrences of a Substring in a String in C - QnA Plus C strchr() Function with example - BeginnersBook ejemplos de causa y efecto en un texto Twitter. C Program to Find Length of String Without using Library Function; How to Implement The Sgn Function in C++? */ #include <stdio.h> /* function : substring . The following C Programming strlwr function will accept the characters as the parameter and convert all the characters in a string to lowercase using the built-in String function Strlwr. Finding substring in string without using library function. C Program to find whether entered string is substring or not without using library function. C Program / Source Code: Here is the source code for strcat() user defined function in C. The function stops reading the input string when it encounters the first character that it does not consider part of a number. strlwr (chars) The strcpy() function also returns the copied string. C stricmp() - 2braces C strcpy() - C Standard Library - Programiz Mainly there are three ways to reserve a given string: By using the new character array. Pattern matching refers to find the position where a string pattern appears in a given string. In my opinion if you know a clever versions exists is enough (because in real life I would Google "efficient strstr implementation") if you happen to know the name even .