題目:
Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]" are not.
思路:
檢查輸入的字串的括號是否有成對出現.
此種類型透過堆疊能夠快速且有效地進行比較.
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public static boolean isValid(String s) { Stack<Character> stack = new Stack<>(); if(s.length()%2!=0) return false; for(int i=0;i<s.length();i++){ char c = s.charAt(i); if(c == '(') stack.push(')'); else if(c == '[') stack.push(']'); else if(c == '{') stack.push('}'); else{ if(stack.isEmpty()) return false; char t = stack.pop(); if(t != c) return false; } } if(stack.empty()) return true; else return false; } |
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