Write a C program to print the message in reverse order using for loop in strings

Here we write a program to reverse the sentence without predefined functions. By using for loop, we can easily print statement in reverse order.

Syntax

for(initialization; condition; increment/decrement) {
    // Read characters
}
for(reverse_initialization; reverse_condition; reverse_increment) {
    // Print characters in reverse
}

Method 1: Character-by-Character Input Using getchar()

This approach reads each character individually using getchar() and stores them in an array. Then it prints the characters in reverse order −

#include <stdio.h>
int main() {
    char stmt[100];
    int i;
    printf("Enter the message:<br>");
    for(i = 0; i < 99; i++) {
        stmt[i] = getchar(); /* reading each char from console till enter or newline char is pressed */
        if(stmt[i] == '<br>')
            break;
    }
    printf("The reverse statement is:<br>");
    for(i--; i >= 0; i--) /* printing each char in reverse order */
        putchar(stmt[i]);
    putchar('<br>');
    return 0;
}

Enter the message:
Hi welcome to my world
The reverse statement is:
dlrow ym ot emoclew iH

Method 2: Using fgets() for Safe Input

Here, we use fgets() instead of getchar() for safer string input handling −

#include <stdio.h>
#include <string.h>
int main() {
    char string[100];
    int length, i;
    printf("Enter string to be reversed: ");
    fgets(string, sizeof(string), stdin);
    
    length = strlen(string);
    /* Remove newline character if present */
    if(string[length - 1] == '<br>') {
        string[length - 1] = '\0';
        length--;
    }
    
    printf("The reversed string is: ");
    for(i = length - 1; i >= 0; i--) {
        putchar(string[i]);
    }
    putchar('<br>');
    return 0;
}

Enter string to be reversed: Hi welcome to tutorials Point
The reversed string is: tnioP slairotut ot emoclew iH

Key Points

• Method 1 uses getchar() for character-by-character input without any string functions.
• Method 2 uses fgets() which is safer than gets() as it prevents buffer overflow.
• Both methods use for loops to reverse the string without using library functions like strrev().
• Time complexity is O(n) where n is the length of the string.

Conclusion

String reversal using for loops provides a fundamental understanding of array manipulation and character handling in C. The fgets() method is recommended for production code due to its safety features.