
Desicription
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.
Solution
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class { public: bool isValid(string s) { stack<char> res; for(int i = 0; s[i]; i++){ if(s[i] == '(' || s[i] == '[' || s[i] == '{') res.push(s[i]); else if(s[i] == ')'){ if(res.empty() || res.top() != '(') return 0; else res.pop(); } else if(s[i] == ']'){ if(res.empty() || res.top() != '[') return 0; else res.pop(); } else if(s[i] == '}'){ if(res.empty() || res.top() != '{') return 0; else res.pop(); } } return res.empty(); } };
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