parentheses balanced in C language [closed] - parentheses

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This is a parentheses balanced code. I submitted and got comment from my professor.
"Your stack is supposed to grow and shrink dynamically to accommodate any number of characters. DO NOT USE scanf for %s, this is risky behavior and Dr. Adams does not approve. Write a helper function to read in characters until newline."
Can you help me to fix this problem?

Answer 1

Your professor is correct and he gave you the solution: do not read a line into a buffer with scanf("%s",...): an arbitrary long line will cause a buffer overflow. You do not need to read a full line, just make check_balanced read one character at a time:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "stack.h"
#define TRUE 1
#define FALSE 0
int check_matching(void);
int main(int argc, char *argv[]) {
int n, i, c;
/* get the number of cases */
if (scanf("%d", &n) != 1) {
printf("invalid number\n");
exit(1);
}
/* consume the rest of the line */
while ((c = getchar()) != EOF && c != '\n')
continue;
for (i = 0; i < n; i++) {
if (check_matching()) {
printf("yes\n");
} else {
printf("no\n");
}
}
return 0;
}
int check_matching(void) {
int ret = TRUE, symbol, checkSymbol;
LinkedStack *pStack;
StackNode *pNode;
StackNode node;
pStack = createLinkedStack();
if (pStack == NULL) {
printf("createLinkedStack failed\n");
exit(1);
}
/* read a full line, one byte at a time */
while ((symbol = getchar()) != EOF && symbol != '\n') {
if (ret == FALSE)
continue;
switch (symbol) {
case '(':
case '[':
case '{':
node.data = symbol;
pushLS(pStack, node);
break;
case ')':
case ']':
case '}':
pNode = popLS(pStack);
if (pNode == NULL) {
ret = FALSE;
break;
} else {
checkSymbol = pNode->data;
if ((symbol == ')' && checkSymbol == '(')
|| (symbol == ']' && checkSymbol == '[')
|| (symbol == '}' && checkSymbol == '{')) {
// Right case. do nothing.
} else {
ret = FALSE;
}
free(pNode);
}
break;
}
}
if (isLinkedStackEmpty(pStack) == FALSE) {
ret = FALSE;
}
deleteLinkedStack(pStack);
return ret;
}