LeetCode-in-All
20. Valid Parentheses
Easy
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 <= 104sconsists of parentheses only'()[]{}'.
Solution
/**
* @param {string} s
* @return {boolean}
*/
var isValid = function (s) {
const stack = []
for (let c of s) {
if (c === '(' || c === '[' || c === '{') {
stack.push(c)
} else if (c === ')' && stack.length > 0 && stack[stack.length - 1] === '(') {
stack.pop()
} else if (c === '}' && stack.length > 0 && stack[stack.length - 1] === '{') {
stack.pop()
} else if (c === ']' && stack.length > 0 && stack[stack.length - 1] === '[') {
stack.pop()
} else {
return false
}
}
return stack.length === 0
}
export { isValid }