题目描述:
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.
这道题利用数据结构栈能够大幅度提高速度,速度能到所有提交的题目中的前2%,看来要想取得理想的速度必须牺牲一定的空间,采用特定的数据结构,算法的思想还是朴素的,但是换了表达形式提升很大了。
class Solution {
public:
bool isValid(string s) {
char temp;
stack<char> Stack;
for(int i=0;i<s.size();i++){
switch(s[i]){
case '(':
case '[':
case '{':
Stack.push(s[i]);
break;
case ')':
if(!Stack.empty()&&Stack.top()=='(')
Stack.pop();
else
return false;
break;
case ']':
if(!Stack.empty()&&Stack.top()=='[')
Stack.pop();
else
return false;
break;
case '}':
if(!Stack.empty()&&Stack.top()=='{')
Stack.pop();
else
return false;
break;
}
}
if(Stack.empty()){
return true;
}else{
return false;
}
}
};