CODEWITHSUNDEEP
cstringpointers
Eo Riendeau
Eo Riendeau

Reputation: 3

Char pointer values changing in loop, but not after

I am currently confused about the execution of my basic c program to reverse a string. I use pointers. Keep in mind that my procedure is most definitely not the most efficient, I simply want to experiment pointers. The problem I have is the following:

// initialize variables
char *sentence = malloc(256);
char *answer = malloc(256);

// ask user for input
printf("please enter sentence\n");
scanf("%s", sentence);

// loop to reverse the "sentence" string
    for (int index = count; index >=0; index--) // count has been determined as the length of the string "sentence" previously
{
    reversed = &sentence[index]; // pointer reversed points to last location of pointer sentence
    printf("\n ** %c", *reversed);
    reversed++; // incremend reversed by 1
}
printf("\n%s", reversed); // prints the cahr pointer reversed as string

Console result If you cannot open the image, what I get is all the character printed in reverse order in the printf in the loop. However the final printf gives a weird result: ( If my sentence is bonjour) \n ** r ** u ** o ** j ** n ** o ** b .
onjour <-- This is what I don't understand.

Thank you for your help, very appreciated.

Upvotes: 0

Views: 269

Answers (2)

jm marti
jm marti

Reputation: 1

reversed = &sentence[index];

That's wrong, I think. 

reversed = sentence[index];

would be right. Anyway that code is messy everywhere.

Upvotes: -1

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726987

The code that prints the string character-by-character in reverse does not store the result in the answer. You need to do it by first pointing reversed to answer, and then adding characters to it as you progress through your loop:

char *reversed = answer;
for (int index = count; index >=0; index--) {
    *reversed = sentence[index];
    printf("\n ** %c", *reversed);
    reversed++;
}
*reversed = '\0';
printf("\n%s", answer);

Upvotes: 2

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