C Exercises: Check if a given string is valid or not

Last update on August 09 2025 12:47:47 (UTC/GMT +8 hours)

10. Valid Parentheses String Check Variants

Write a C program to check if a given string is valid or not. The string contains the characters '(', ')', '{', '}', '[' and ']'. The string is valid if the open brackets must be closed with the same type of bracket and in the correct order.

C Code:

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
static bool is_valid_Parentheses(char *s)
{
    int n = 0, cap = 100;
    char *tstack = malloc(cap);

    while (*s != '\0') {
        switch(*s) {
        case '(':
        case '[':
        case '{':
            if (n + 1 >= cap) {
                cap *= 2;
                tstack = realloc(tstack, cap);
            }
            tstack[n++] = *s;
            break;
        case ')':
            if (tstack[--n] != '(') return false;
            break;
        case ']':
            if (tstack[--n] != '[') return false;
            break;
        case '}':
            if (tstack[--n] != '{') return false;
            break;
        default:
            return false;
        }
        s++;
    }
    return n == 0;
}
int main(void)
  {
	//char **vbracket = "()[]{}";
	char **vbracket = "([)]";
	printf("%s\n", is_valid_Parentheses(vbracket) ? "true" : "false");
    return 0;
}

Sample Output:

false

Flowchart:

For more Practice: Solve these Related Problems:

Write a C program to check if a string of various types of brackets is valid using a stack data structure.
Write a C program to validate a parentheses string and output the position of the first unmatched bracket.
Write a C program to verify the validity of a string containing nested and sequential brackets, ignoring non-bracket characters.
Write a C program to check the validity of a mixed parentheses string using a recursive function.

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