我的代码没有正确反转每个单独单词的字符串？

Question

I am doing an assignment where I have to implement a function reverse() that reverses the string between indexes i and j inclusively. reverse(str, 0, 4) will reverses the string between indexes of 0 and 4 from apple to elppa.All words can be reversed by finding start and end positions of each word and reversing the word.

void reverse(char *str, int i, int j). for example

userinput:

apple orange banana

will output:

elppa egnaro ananab

but my code prints nothing. I know thereare a lot of bugs but I am stuck and don't know how to go from here. My code is:

#include <stdio.h>
#include <string.h>
void reverse(char *str, int i, int j);
int i, j, k, len, ind, temp;
char str[100];
int main()
{

    printf("Enter a string: \n");
    gets(str);
    len = strlen(str);
    reverse(str, i, j);
    return 0;
}
void reverse(char *str, int i, int j)
{
    for (i = 0; i < len; i++)//
    {
        ind = i;
            //index of the end of each word
        if (str[i] == ' ' || str[i] == '\n')//ends at index of whites space
        {
            ind = i - 1;//index of empty space -1
            i= 0;//i is reset to 0
            if (i <= ind)//0<last index of word
            {
                //reverse
                temp = str[i];
                str[i] = str[ind];
                str[ind] = temp;
            }
        }
      }
   printf("%s\n",str[i]);
}

Answer 1

Sorry, but your code is really broken. I don't really know how to "fix" it without basically rewriting it from scratch. The first most obvious is this:

void reverse(char *str, int i, int j)
{
    for (i = 0; i < len; i++)

You're throwing away whatever was in the variable i by initializing it to zero. So this function will do the same thing irregardless of the value if i .

You are also using a lot of global variables for no good reason. NEVER use globals unless you have a good reason, and this is not one of them. Move the declaration of i, j, k, len, ind and temp inside the body of reverse. Move declaration of str inside main.

The variable j is never used.

NEVER use the function gets . It has been removed from modern C.

printf("%s\\n",str[i]); makes no sense. You're trying to print the i:th character, but as a string. This is undefined behavior.

Turn on compiler warnings. This is what I got when I compiled your code:

$ gcc b.c -Wall -Wextra
b.c: In function ‘main’:
b.c:10:5: warning: implicit declaration of function ‘gets’; did you mean ‘fgets’? [-Wimplicit-function-declaration]
     gets(str);
     ^~~~
     fgets
b.c: In function ‘reverse’:
b.c:34:13: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Wformat=]
    printf("%s\n",str[i]);
            ~^    ~~~~~~
            %d
b.c:15:36: warning: unused parameter ‘j’ [-Wunused-parameter]
 void reverse(char *str, int i, int j)
                                ~~~~^

Answer 2

The first programming principle to apply here is decomposition . You have two tasks: identify the words in the input string, and reverse the letters of each word. Trying to do both together is much more difficult than doing either one.

First write a function that will reverse one word, given its start and end indexes, then write a second function that will identify the words and call the first function to reverse them. You can finish and test the first function before you attempt the second.