I have written a balanced symbol checker with stacks. Everything else works and I have fully tested all functions like pop push destroy isempty. The problem is my fgets usage.
//fgets
char input[10];
printf("Enter a 10 character input for balance: ");
fgets(input, 10, stdin);
the part that is "not working" is the following code
int i = 0;
for (i < 10; i++;){
if (input[i] == '{' || input[i] == '[' || input[i] == '(' || input[i] == '<'){
push(&st2, input[i]);
}
}
I know my push function is working, because i have tested it as a standalone. something like:
push(&st2, '{');
works perfectly fine when i try to display my stack and correctly pushes the value. At this point I am thinking that either the initial char array with fgets is just not initializing correctly, or I have somehow managed to screw up the if/for loop.
When I run the program the if statement conditional is never met even if i type a { [ ( or < into stdin. When I try to print our the input[10] char array my program just crashes aswell.
The for loop is wrong.
Try
int i;
for (i = 0; i < 10; i++) {
...
}
instead.
The correct syntax is
for (initialisation; condition; increment) {
body
}
So if you write this:
int i = 0;
for (i < 10; i++; ) {
...
}
the following happens:
First the initialisation occurs. i < 10
is executed, but it is a simple logical expression which evaluates to true
and is ignored. Then the condition is checked. i++
evaluates to 0 (not to 1, because of the post -increment), which is interpreted as false
and the loop terminates.
There are a lot of problems in your code.
1)
char input[10];
printf("Enter a 10 character input for balance: ");
Should be:
char input[11];
You need the '\\0' too.
2)
fgets(input, 10, stdin);
Always check return:
if (fgets(input, 10, stdin) != NULL){}
3)
for (i < 10; i++;){}
Is wrong, it should be:
for (;i < 10; i++){}
Do you see the difference ?
Now we can put them all together:
#include<stdio.h>
#include<stdlib.h>
int main(void){
char input[11];
int i = 0;
printf("Enter a 10 character input for balance: ");
if (fgets(input, 10, stdin) != NULL){
for (;i < 10; i++){
/* do what you need here */
}
}
printf("Goodbye\n");
return 0;
}
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