Matching Parentheses in C language(not cpp nor c#)

The following program is written by other chegg expert but it has bug.

#include

#include

#include

#define MAX_LENGTH 100

typedef struct {

char c;

int pos;

} Paren;

int is_match(char c1, char c2) {

return (c1 == '(' && c2 == ')') ||

(c1 == '[' && c2 == ']') ||

(c1 == '{' && c2 == '}');

}

int main(int argc, char *argv[]) {

if (argc != 3) {

printf("Usage: %s input_file output_file ", argv[0]);

return 1;

}

FILE *fin = fopen(argv[1], "r");

if (!fin) {

printf("Cannot open input file: %s ", argv[1]);

return 1;

}

FILE *fout = fopen(argv[2], "w");

if (!fout) {

printf("Cannot open output file: %s ", argv[2]);

return 1;

}

Paren stack[MAX_LENGTH];

int top = 0;

char buffer[MAX_LENGTH];

int pos = -1;

fgets(buffer, MAX_LENGTH, fin);

for (int i = 0; i

char c = buffer[i];

if (c == '(' || c == '[' || c == '{') {

stack[top].c = c;

stack[top].pos = i;

top++;

} else if (c == ')' || c == ']' || c == '}') {

top--;

if (top

pos = i;

break;

}

}

}

if (top == 0 && pos == -1) {

fprintf(fout, "There are %d balanced parentheses. ", (int)strlen(buffer) / 2);

} else {

fprintf(fout, "Error is spot at position %d at first. ", pos);

}

fclose(fin);

fclose(fout);

return 0;

}

Sample 2 has error The wrong output of the program is Error is spot at position -1 at first. which is wrong

Sample 1 Input: (())()

Sample 1 Output: There are 3 balanced parentheses.

Sample 2 Input: (())(

Sample 2 Output: Error is spot at position 5 at first.

Sample 3 Input: (())()()

Sample 3 Output: There are 4 balanced parentheses.

Sample 4 Input: [{]}

Sample 4 Output: Error is spot at position 2 at first.

Please use FILE*, fopen, fclose, fscanf and fprintf as both input and output are inside a .txt file. If you think it is inconvenient, you can use your way.

You are going to write a program to check whether the parentheses are balanced or not. For example, "( ( ) ) ( ) " is a balanced parentheses, while "( ( ) ) (" and "( ( ) ) )" are unbalanced. There are three types of parentheses, which are ( ), [] and \{\} . If the parentheses are balanced, you need to output the number of matching parentheses. If the parentheses are unbalanced, you need to output the first position (zero-based) that you spot error. Your program should read the input from the file, and output the answer to another file. The first argument is the input file name, while the second argument is the output file name. Name your program as "lab3-q3.c". Input file: A string contains ( ), [ ] and \{\} only. The length of input will not exceed 100 characters. Output file: If the parentheses are balanced, output "There are X balanced parentheses." If the parentheses are unbalanced, output "Error is spot at position Y at first." Y is a zero-based number. Sample 1 Input: (())() Sample 1 Output: There are 3 balanced parentheses. Sample 2 Input: (())( Sample 2 Output: Error is spot at position 5 at first