Leetcode - Valid Parenthesis

valid_parenthesis.rs

// Problem link -> https://leetcode.com/problems/valid-parentheses/

fn main() {
    assert_eq!(Solution::is_valid("()".to_string()), true);
    assert_eq!(Solution::is_valid("()[]{}".to_string()), true);
    assert_eq!(Solution::is_valid("(]".to_string()), false);
    assert_eq!(Solution::is_valid("([)]".to_string()), false);
    assert_eq!(Solution::is_valid("{[]}".to_string()), true);
    assert_eq!(Solution::is_valid("]".to_string()), false);
}

enum Solution {}
use std::collections::{VecDeque, HashMap};

impl Solution {
    pub fn is_valid(s: String) -> bool {
        let mut sv : Vec<char> = s.chars().collect();
        let mut stack = VecDeque::new();
        let mut map = HashMap::new();
        map.insert(')','(');
        map.insert(']','[');
        map.insert('}','{');
        let mut flag = true;
        let mut counter = 0;
        
        for c in sv.into_iter() {
            match c {
                '(' | '[' | '{' => {stack.push_front(c); counter += 1;},
                ')' | ']' | '}' => {
                    if let Some(x) = stack.pop_front() {
                        if let Some (&ch) = map.get(&c) {
                            if ch != x {
                                flag = false;
                                break;
                            } else {
                                counter -= 1;
                            }
                        } else {
                            panic!("This is not part of the bracket map");
                        }
                    } else {
                        flag = false;
                        counter = -1;
                        break;
                    }
                },
                _ => panic!("This is not a bracket"),
            }
        }
        
        if counter == 0 {
            flag = true;
        } else {
            flag = false;
        }
        
        flag
    }
}