Given a string 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.
Note that an empty string is also considered valid.
Example 1:
Input: "()"
Output: true
Example 2:
Input: "()[]{}"
Output: true
Example 3:
Input: "(]"
Output: false
Example 4:
Input: "([)]"
Output: false
Example 5:
Input: "{[]}"
Output: true
Solution:
stack. pop if closing match stack top.
class Solution {
public:
bool isValid(string s) {
stack<char> st;
for(char c : s){
if(!st.empty()){
char x = st.top();
if((x == '(' && c==')') || (x=='[' && c==']') || (x=='{' && c == '}')){
st.pop(); continue;
}
}
st.push(c);
}
return st.empty();
}
};