20.有效的括号 - 小趴菜菜籽 - 沸点 - 掘金

学生

#每日一题#
20.有效的括号
public boolean isValid(String s) {
HashMap<Character,Character> map = new HashMap<Character,Character>();
map.put('(',')');
map.put('{','}');
map.put('[',']');
map.put('?','?');//放置map中找不到，报出空指针异常
int len = s.length();
Stack<Character> stack = new Stack<Character>();
stack.add('?');
if(len==1)return false;
for(int i=0;i<len;i++){
if(map.containsKey(s.charAt(i)))stack.push(s.charAt(i));
else{

if(s.charAt(i)==map.get(stack.peek())){
stack.pop();
}
else {
return false;
}
}
System.out.println(stack.size());
}
return stack.size()==1;
}

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