Reading and reversing string using getchar in C - c

Question

New C coder here. I'm not certain why, but my program gets stuck in the first while loop and will not move on to the other code. Does anyone have any idea what's wrong?
#include <stdio.h>
int main(void){
char str[20];
char reverse[20];
int c;
int i;
int j;
int k;
printf("Enter a string: ");
i=0;
j=0;
while((i<20)&&((c=getchar())!='\n')){
str[i] = c;
i++;
}
k=i;
while((j<k)&&(i>=0)){
reverse[j]=str[i];
j++;
i--;
}
printf("\n");
if(i==0){
while(i<k){
putchar(reverse[i]);
}
}else{
printf("logic error");
}
return 0;
}
Thank you!

Answer 1

#include<stdio.h>
void reverse(void)
{
char c;
if((c = getchar()) != '\n'){ reverse(); }
putchar(c);
return;
}
int main(void)
{
printf("Enter a line of text below:n");
reverse();
putchar('\n');
}

Answer 2

Your code don't get stuck in the first while. It gets stuck here:
while(i<k){
putchar(reverse[i]);
}
because you never change i or k, i.e. an endless loop.
Try this instead:
while(i<k){
putchar(reverse[i]);
++i;
}
Another problem is that you reverse one character past the input as i has been incremented to index the "next free char" . Don't do that.
Instead of:
while((j<k)&&(i>=0)){
reverse[j]=str[i];
j++;
i--;
}
try:
while(i>=0){
reverse[j]=str[i-1]; // Notice the -1
j++;
i--;
}
++i;
Putting it all together, it will be:
int main(void){
char str[20];
char reverse[20];
int c;
int i;
int j = 0;
int k;
printf("Enter a string: ");
i=0;
j=0;
while((i<20)&&((c=getchar())!='\n')){
str[i] = c;
i++;
}
k=i;
while(i >= 0){
reverse[j]=str[i-1]; // Notice
j++;
i--;
}
++i; // Notice
printf("\n");
if(i==0){ // This if-statement is nor really needed - just remove it
while(i<k){
putchar(reverse[i]);
i++; // Notice
}
}else{
printf("logic error");
}
printf("\n");
return 0;
}