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.
括号匹配的问题,使用栈解决。(注意,访问栈元素时要先判断栈是否为空)
C++实现代码如下:
#include<iostream> #include<string> #include<stack> using namespace std; class Solution { public: bool isValid(string s) { size_t index=0; stack<char> ss; while(index<s.length()) { char c; switch(s[index]) { case '(' : case '[' : case '{' : ss.push(s[index]); break; case ')' : if(ss.empty()) return false; c=ss.top(); if(c!='(') return false; ss.pop(); break; case ']' : if(ss.empty()) return false; c=ss.top(); if(c!='[') return false; ss.pop(); break; case '}' : if(ss.empty()) return false; c=ss.top(); if(c!='{') return false; ss.pop(); break; default: return false; } index++; } if(index==s.length()&&ss.empty()) return true; return false; } }; int main() { string str="]"; Solution s; cout<<s.isValid(str)<<endl; }
运行结果:
#include<string> #include<iostream> #include<stack> using namespace std; class Solution { public: bool isValid(string s) { stack<char> st; int i; for(i=0;i<(int)s.size();i++) { switch(s[i]) { case '(': case '[': case '{': st.push(s[i]); break; case ')': if(st.empty()||st.top()!='(') return false; st.pop(); break; case ']': if(st.empty()||st.top()!='[') return false; st.pop(); break; case '}': if(st.empty()||st.top()!='{') return false; st.pop(); break; } } if(st.empty()) return true; else return false; } }; int main() { Solution s; string str="((()))"; cout<<s.isValid(str)<<endl; }