Valid Parentheses
Updated: Jan 20, 2021
Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if:
Open brackets must be closed by the same type of brackets.
Open brackets must be closed in the correct order.
Example 1: Input: s = "()" Output: true Example 2: Input: s = "()[]{}" Output: true Example 3: Input: s = "(]" Output: false Example 4: Input: s = "([)]" Output: false Example 5: Input: s = "{[]}" Output: true Constraints:
1 <= s.length <= 104
s consists of parentheses only '()[]{}'.
Solution:
class Solution {
public boolean isValid(String s) {
Map<Character,Character> map = new HashMap<Character,Character>();
Stack<Character> stack = new Stack<>();
map.put('}','{');
map.put(']','[');
map.put(')','(');
for(char c:s.toCharArray())
{
if(map.containsKey(c))
{
if(!stack.isEmpty())
{
if(stack.pop()!=map.get(c)) return false;
}
else
return false;
}
else
stack.push(c);
}
return stack.isEmpty();
}
}