class Solution {
public:
bool checkValidString(string s) {
int low = 0, high = 0;
for (char c : s) {
if (c == '(') {
low++; high++;
} else if (c == ')') {
low = max(0, low - 1);
high--;
} else { // '*'
low = max(0, low - 1);
high++;
}
if (high < 0) return false;
}
return low == 0;
}
};
