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.Every close bracket has a corresponding open bracket of the same type. Example 1:Input: s = "()"Output: trueExample 2:Input: s = "()[]{}"Output: trueExample 3:Input: s = "(]"Output: false Constraints:1 <= s.length <= 104s consists of parentheses only '()[]{}'.
Question
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.Every close bracket has a corresponding open bracket of the same type. Example 1:Input: s = "()"Output: trueExample 2:Input: s = "()[]{}"Output: trueExample 3:Input: s = "(]"Output: false Constraints:1 <= s.length <= 104s consists of parentheses only '()[]{}'.
Solution
To solve this problem, we can use a stack data structure. Here are the steps:
- Initialize an empty stack.
- Iterate over each character in the string.
- If the character is an open bracket (i.e., '(', '{', or '['), push it onto the stack.
- If the character is a close bracket (i.e., ')', '}', or ']'), check if the stack is empty. If it is, return false because there's no corresponding open bracket.
- If the stack is not empty, pop the top element from the stack and check if it matches with the close bracket. If it doesn't, return false.
- After iterating over all characters in the string, check if the stack is empty. If it's not, return false because there are unmatched open brackets.
- If the stack is empty, return true because all brackets are properly matched and nested.
Here is a Python code snippet that implements these steps:
def isValid(s):
stack = []
bracket_map = {")": "(", "}": "{", "]": "["}
for char in s:
if char in bracket_map:
top_element = stack.pop() if stack else '#'
if bracket_map[char] != top_element:
return False
else:
stack.append(char)
return not stack
In this code, bracket_map is a dictionary that maps each close bracket to its corresponding open bracket. For each character in the string, if it's a close bracket, we pop the top element from the stack and check if it's the corresponding open bracket. If it's not, we return false. If the character is an open bracket, we push it onto the stack. After iterating over all characters, we check if the stack is empty. If it's not, there are unmatched open brackets, so we return false. If the stack is empty, all brackets are properly matched and nested, so we return true.
Similar Questions
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