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Valid Parentheses.cpp
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Valid Parentheses.cpp
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/*左括号直接进栈,右括号直接与栈顶元素比较。*/
class Solution {
public:
bool isValid(string s){
stack<char> st;
for(int i=0;i<s.length();i++){
if(s[i]=='('||s[i]=='{'||s[i]=='[')
st.push(s[i]);
else if(s[i]==')'){
if(st.empty())
return false;
else if(st.top()=='('){
st.pop();
}else{
return false;
}
}else if(s[i]=='}'){
if(st.empty())
return false;
else if(st.top()=='{'){
st.pop();
}else{
return false;
}
}else if(s[i]==']'){
if(st.empty())
return false;
else if(st.top()=='['){
st.pop();
}else{
return false;
}
}
}
if(st.empty())
return true;
else
return false;
}
};