leetcode题解:Valid Parentheses(栈的应用-括号匹配)
题目:
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.
说明:
1)括号可嵌套,如{[()]}
实现:
1 class Solution { 2 public: 3 bool isValid(string s) { 4 if(s.empty()) return false;//空字符串,false 5 int len=strlen(s.c_str()); 6 if(len==1) return false;//只有一个字符,false 7 char pre; 8 stack<char> char_stack; 9 for(int i=0;i<len;i++) 10 { 11 if(isPop(s[i])) //该出栈顶元素 12 { 13 if(!char_stack.empty()) 14 { 15 pre=char_stack.top();//取栈顶元素、并出栈 16 char_stack.pop(); 17 if(!isChar(pre,s[i]))//是否匹配 18 return false; 19 } 20 else return false; 21 } 22 else //入栈 23 { 24 char_stack.push(s[i]); 25 } 26 } 27 return char_stack.empty();//栈空true,否则false 28 } 29 private: 30 bool isPop(char t) //判断是否是)} ]符号,是则出栈栈顶元素 31 { 32 if(t==')'||t=='}'||t==']') 33 return true; 34 else 35 return false; 36 } 37 bool isChar(char t1,char t2)//判断两字符t1,t2是否匹配 38 { 39 switch (t1) 40 { 41 case '(': 42 { 43 if(t2==')') return true; 44 else return false; 45 break; 46 } 47 case '{': 48 { 49 if(t2=='}') return true; 50 else return false; 51 break; 52 } 53 case '[': 54 { 55 if(t2==']') return true; 56 else return false; 57 break; 58 } 59 default: 60 return false; 61 } 62 } 63 };