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20_valid_parentheses.cpp
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20_valid_parentheses.cpp
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//Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
//An input string is valid if:
// Open brackets must be closed by the same type of brackets.
// Open brackets must be closed in the correct order.
// Every close bracket has a corresponding open bracket of the same type.
//Example 1:
//Input: s = "()"
//Output: true
//Example 2:
//Input: s = "()[]{}"
//Output: true
//Example 3:
//Input: s = "(]"
//Output: false
//Constraints:
// 1 <= s.length <= 104
// s consists of parentheses only '()[]{}'.
class Solution {
public:
bool isValid(string s) {
stack<char> openBrackets;
for (int i = 0; i < s.size(); i++) {
if (s[i] == '(' || s[i] == '{' || s[i] == '[') {
openBrackets.push(s[i]);
} else {
if (openBrackets.empty())
return false;
char topBracket = openBrackets.top();
openBrackets.pop();
if ((s[i] == ')' && topBracket == '(') ||
(s[i] == '}' && topBracket == '{') ||
(s[i] == ']' && topBracket == '[')
) {
continue;
} else {
return false;
}
}
}
return openBrackets.empty();
}
};