Valid Parentheses Given a string 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. Note that an empty string is also considered valid.
Example 1:
Input: “()” Output: true
Example 2:
Input: “()[]{}” Output: true
Example 3:
Input: “(]” Output: false
Example 4:
Input: “([)]” Output: false
Example 5:
Input: “{[]}” Output: true
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 class Solution { public boolean isValid (String s) { char [] charArray = s.toCharArray(); Stack<Integer> stack = new Stack<>(); if (s == null || s.length() == 0 ) { return true ; } for (int i = 0 ; i < charArray.length; i++) { if (trans(charArray[i]) > 0 ) { stack.push(trans(charArray[i])); } else if (trans(charArray[i]) < 0 ) { if (!stack.isEmpty() && stack.pop() + trans(charArray[i]) == 0 ) { continue ; } else { return false ; } } else { return false ; } } if (stack.size() == 0 ) { return true ; } else { return false ; } } private int trans (char c) { switch (c) { case '(' : return 1 ; case ')' : return -1 ; case '[' : return 2 ; case ']' : return -2 ; case '{' : return 3 ; case '}' : return -3 ; default : return 0 ; } } }
Source code is easy to see.
Referencehttps://leetcode-cn.com/problems/valid-parentheses