Reversing a string

[Firestone]

I'm trying to write a program to reverse a string, letter by letter. This was my latest attempt:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void)
{
    char oldMsg[100], newMsg[100];
    int cd = 12, cu = 0;
    strcpy(newMsg, "Hello World!");
    while (cd > 0)
    {
          newMsg[cu] = oldMsg[cd];
          cu++;
          cd--;
    }
    printf("%c", newMsg);
    printf("\n\nPress ENTER to end . . .");
    getchar();
    return 0;
}

The final message is a 'p', which I'm not sure where it came from. Can I get some help please?

[thekashyap]

Problem is you're copying old to new, whereas what you want to do is new to old. Also using wrong formatting in printf().

See the comments inside the code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

//to avoid hard coding.
#define MY_MSG_LEN 100

int main(void)
{
    char oldMsg[MY_MSG_LEN], newMsg[MY_MSG_LEN];
    int len_newMsg = 0, i ;
    //not required to hardcode the length of "Hello World!", use strlen() instead
    //int cd = 12, cu = 0;
    strcpy(newMsg, "Hello World!");

    // -1 to discount the null char, which we'll still like to have at the end
    //and not at the begenning of oldMsg.
    len_newMsg = strlen( newMsg ) - 1 ;

//copy the other way around.
/*    while (cd > 0)
    {
          newMsg[cu] = oldMsg[cd];
          cu++;
          cd--;
    }
*/
    for( i = 0; i <= len_newMsg; i++ )
       oldMsg[i] = newMsg[len_newMsg-i] ; //copy backwards

    //last char should be a null char
    oldMsg[len_newMsg+1] = '\0' ;

    //%c is for a single character, %s is for a c-style char string
    //printf("%c", newMsg);
    printf("%s", oldMsg);

    printf("\n\nPress ENTER to end . . .");
    getchar();

    return 0;
}

[ranjani]

hi this is the program without using any string builtin function......

/* C program without using string functions*/
#include<stdio.h>
#include<conio.h>
void main()
{
clrscr();
char str1[20],str2[20],c;
int i,j,count=0,k;
printf("Enter the String");
i=0;
while((c=getchar())!='\n')
{
str1[i]=c;
i++;
count++;
}
str1[i]='\0';
j=0;
for(i=count-1;i>=0;i--)
{
str2[j]=str1[i];
j++;
}
str2[j]='\0';
printf("string1 = %s\nstring2 = %s",str1,str2);
getch();
}

[Narue]

ranjani, I'm going to ask you nicely just once to use code tags when you post code. Code tags put your code in a nice block and retain any formatting you had. Not using them makes your code an awful mess that nobody wants to read.

[ranjani]

:)

ranjani, I'm going to ask you nicely just once to use code tags when you post code. Code tags put your code in a nice block and retain any formatting you had. Not using them makes your code an awful mess that nobody wants to read.

you mean like this attractives?

/* C program without using string functions*/
#include<stdio.h>
#include<conio.h>
void main()
{
clrscr();
char str1[20],str2[20],c;
int i,j,count=0,k;
printf("Enter the String");
i=0;
while((c=getchar())!='\n')
{
str1[i]=c;
i++;
count++;
}
str1[i]='\0';
j=0;
for(i=count-1;i>=0;i--)
{
str2[j]=str1[i];
j++;
}
str2[j]='\0';
printf("string1 = %s\nstring2 = %s",str1,str2);
getch();
}

or can you give some model? i am a new one for this forum

[Narue]

>or can you give some model?
The text editor has a watermark that tells you exactly how to use code tags. I don't know how you could miss that, but here's a link to instructions you can't miss.

[Firestone]

Ok, I see what I was doing wrong. Thanks for the help.