[Leetcode] Valid Parentheses
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.
Solution:
1 public class Solution { 2 public boolean isValid(String s) { 3 if (s == null || s.length() == 0) 4 return true; 5 if (s.length() == 1) 6 return false; 7 int N = s.length(); 8 int i = 0; 9 Stack<Character> myStack = new Stack<Character>(); 10 while (i < N) { 11 char temp = s.charAt(i); 12 if (temp == '(' || temp == '{' || temp == '[') { 13 myStack.push(temp); 14 i++; 15 } else { 16 if (!myStack.isEmpty()) { 17 char t = myStack.pop(); 18 if (((t == '(') && (temp == ')')) 19 || ((t == '{') && (temp == '}')) 20 || ((t == '[') && (temp == ']'))) { 21 i++; 22 } else { 23 return false; 24 } 25 } else { 26 return false; 27 } 28 } 29 } 30 if(myStack.isEmpty()) 31 return true; 32 else 33 return false; 34 } 35 }
我的代码风格太差了,贴一下大神的代码:
1 public class Solution { 2 public boolean isValid(String s) { 3 if (s == null) 4 return false; 5 Stack st = new Stack(); 6 for (int i = 0; i < s.length(); i++) { 7 if(s.charAt(i)==']'||s.charAt(i)==')'||s.charAt(i)=='}'){ 8 if(st.empty()) 9 return false; 10 else{ 11 char c= st.pop().toString().charAt(0); 12 if(!((c=='('&&s.charAt(i)==')')||(c=='['&&s.charAt(i)==']')||(c=='{'&&s.charAt(i)=='}'))){ 13 return false; 14 } 15 } 16 }else{ 17 st.push(s.charAt(i)); 18 } 19 } 20 return st.empty(); 21 } 22 }