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.
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.
Solution
This problem can be solved using 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, the string is not valid, because there's no corresponding open bracket for this close bracket.
- If the stack is not empty, pop the top element from the stack. If the popped element is not the corresponding open bracket for the current close bracket, the string is not valid.
- After iterating over all characters in the string, check if the stack is empty. If it's not, the string is not valid, because there are some open brackets without corresponding close brackets.
- If the string passes all these checks, it is valid.
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:
stack.append(char)
elif not stack or bracket_map[stack.pop()] != char:
return False
return not stack
This function returns True if the string s is valid according to the rules you provided, and False otherwise.
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