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.
1 public class Solution { 2 public boolean isValid(String s) { 3 if(s.length() % 2 == 1)//个数为奇数返回false 4 return false; 5 char stack[] = new char[s.length() / 2]; 6 // boolean isValid = true; 7 int top = -1;//栈顶 8 stack[++top] = s.charAt(0); 9 10 for(int i = 1; i < s.length(); i++){//遍历完成 11 12 if('(' == s.charAt(i) || '[' == s.charAt(i) || '{' == s.charAt(i)){//入栈 13 if(top >= stack.length - 1)//左括号个数大于右括号个数 14 return false; 15 stack[++top] = s.charAt(i); 16 } 17 else{ 18 if(-1 == top){//如果栈已经空了 19 return false; 20 } 21 char temp = stack[top--];//出栈 22 switch(s.charAt(i)){ 23 case ')': 24 if(temp != '(') 25 return false; 26 break; 27 case ']': 28 if(temp != '[') 29 return false; 30 break; 31 case '}': 32 if(temp != '{') 33 return false; 34 } 35 } 36 } 37 if(-1 == top)//栈为空 38 return true; 39 return false;//栈不空 40 } 41 }