Print words in string in reverse order C - c

Question

I take user input using fgets() and store it into a temp array. I then concatenate that to a main array called userInput so that the user can enter multiple lines.
Let's say the user enters the following:
This is a sentence
This is a new line
I need it to print each line in the order they were entered but reverse the order of words like below:
sentence a is This
line new a is This
I have the current approach but I get this:
line
new a is sentence
This a is This
Below is my code where I call reversePrint() with a string to reverse:
void printToSpace(const char *str) {
do {
putc(*str, stdout);
} while(*str++ != ' ');
}
void reversePrint(const char *str) {
const char *p = strchr(str, ' ');
if (p == NULL) {
printf("%s", str);
}
else {
reversePrint(p + 1);
printToSpace(str);
}
}

Answer 1

Here is an alternative way:
#include <stdio.h>
#include <string.h>
void reversePrint(const char *str)
{
if (str)
{
reversePrint(strtok (NULL, " \t\n\r"));
printf("%s ", str);
}
}
int main(void)
{
char string[] = "This is a sentence";
reversePrint(strtok(string, " \t\n\r"));
return 0;
}
It seems so clear and simple that I suspect if strtok() is born for requirements like this.

Answer 2

Here are just a few thoughts...
I feel that using fgets will provide you with an undesired new-line marker. Hence, you need to handle the "\r\n" in the reverse printing function.
I feel that the reverse printing is easier to perform in a single function, although I loved the recursive approach, so I'll use it here.
I should point out that I wouldn't use a recursive function if this was a production application, as we'll be wasting resources and bloating the stack for no good reason.
On a non-recursive approach I would probably use the %.*s format, instead of printing each char separately.
I think your code would work if you only changed printToSpace so that it manages the \n contingency - but I felt like re-writinfg the function. Try this in your solution:
void printToSpace(const char *str) {
do {
putc(*str, stdout);
} while(*str && *str != '\n' && *str != '\r' && *str++ != ' ');
}
Here's my full code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void print_rev(char* str);
// collects two strings and send them to the `print_rev` function
int main(int argc, char const* argv[]) {
char str_array[2][255];
// Get string 1
printf("Enter the first string (up to 255 characters):\n");
fgets(str_array[0], 255, stdin);
printf("Please enter the second string (up to 255 characters):\n");
fgets(str_array[1], 255, stdin);
printf("You entered:\n1. %s2. %s", str_array[0], str_array[1]);
printf("\nString 1 reversed: ");
print_rev(str_array[0]);
printf("\nString 2 reversed: ");
print_rev(str_array[1]);
printf("\n");
}
// prints a string in reverse order.
void print_rev(char* str) {
// find the first occurrence of the ` ` (space)
char* p = strchr(str, ' ');
// if a space exists...
if (p) {
// call `print_rev` for whatever's after the space.
print_rev(p + 1);
// print a space
putc(' ', stdout);
}
// print every character until an EOL, space or NULL is encountered
while (*str && *str != ' ' && *str != '\n' && *str != '\r')
putc(*(str++), stdout);
}

Answer 3

#include <stdio.h>
#include <string.h>
#define MAX_LEN 100000
int main()
{
char str[MAX_LEN], temp[MAX_LEN];
printf("Enter the Sentence to print reverse : ");
scanf("%[^\n]%*c", &str);
int i, left, right, length = strlen(str);
left = 0;
right = length - 1;
printf("%d \n", length);
for(i=0;i<length;i++)
{
temp[i] = str[right];
right--;
}
printf("%s",temp);
return 0;
}