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#include<string>
#include<stack>
#include<iostream>
std::string removeStars(const std::string& s) {
std::stack<char> st;
for (int i = 0; i < s.size(); i++) {
if (s[i] == '*') {
if (st.empty())
throw "invalid expr";
else
st.pop();
}
else
st.push(s[i]);
}
std::string res(st.size(), '\0');
size_t idx = st.size() - 1;
while (!st.empty()) {
res[idx--] = st.top();
st.pop();
}
return res;
}
std::string removeStarsTwo(const std::string& str) {
// As we are using only push_back and pop_back here
// the std::string is equivalent to a stack
// and we save up some time and memory.
std::string result;
for(char c : str) {
if(c == '*') {
result.pop_back();
}
else {
result.push_back(c);
}
}
return result;
}
int main() {
}
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