Given a string str. The task is to find the length of the string.
Examples:
Input: str = "Geeks" Output: Length of Str is : 5 Input: str = "neveropen" Output: Length of Str is : 13
In the below program, to find the length of the string str, first the string is taken as input from the user using scanf in 
, and then the length of Str is calculated using 
and using 
method .
Below is the C program to find the length of the string.
Example 1: Using loop to calculate the length of string.
C
// C program to find the length of string#include <stdio.h>#include <string.h>int main(){ char Str[1000]; int i; printf("Enter the String: "); scanf("%s", Str); for (i = 0; Str[i] != '\0'; ++i); printf("Length of Str is %d", i); return 0;} |
Enter the String: Length of Str is 0
Time Complexity: O(N)
Auxiliary Space: O(1)
Example 2: Using strlen() to find the length of the string.
C
// C program to find the length of // string using strlen function#include <stdio.h>#include <string.h>int main(){ char Str[1000]; int i; printf("Enter the String: "); scanf("%s", Str); printf("Length of Str is %ld", strlen(Str)); return 0;} |
Enter the String: Length of Str is 0
Time Complexity: O(1)
Auxiliary Space: O(1)
Example 3: Using sizeof() to find the length of the string.
C
// C program to find the length of// string using sizeof() function#include <stdio.h>#include <string.h>int main(){ printf("Enter the String: "); char ss[] = "neveropen"; printf("%s\n", ss); // print size after removing null char. printf("Length of Str is %ld", sizeof(ss) - 1); return 0;}// This code is contributed by ksam24000 |
Enter the String: neveropen Length of Str is 5
Time Complexity: O(1)
Auxiliary Space: O(1)
Example 4: Using Pointer Subtraction
C
// C program to find the size of string by pointer// substraction#include <stdio.h>int main(){ char str[] = "Geeks"; char* ptr = str; // traversing till last pointer while (*ptr) { ptr++; } printf("Address of start position of string : %x\n", str); printf("Address of end position of string : %x\n", ptr); // difference between the address will give the length // of string int length = ptr - str; printf("Length of the string: %d\n", length); return 0;}// contributed by puligokulakishorereddy |
Address of start position of string : e996300 Address of end position of string : e996305 Length of the string: 5
Time Complexity: O(n)
Space Complexity: O(1)
Explanation
- In the main() function, a character array str[] is defined and initialized with the string “Greeks“.
- A pointer ptr is declared and initialized with the starting address of the str = e996300 array.
- The code enters a while loop that iterates until the value pointed to by ptr is not null. In C, the null character ‘\0‘ signifies the end of a string.
- Inside the loop, the ptr is incremented to point to the next character in the string.
- After the loop, the code calculates the length of the string by subtracting the starting address of str = e996300 from the final value of ptr = e996305. This pointer subtraction gives the number of elements (characters) between the two addresses
|
G |
e |
e |
k |
s |
\0 |
|---|---|---|---|---|---|
|
e996300 |
e996301 | e996302 | e996303 | e996304 | e996305 |
Note: The address may be different in different execution of the above program.
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