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1.4.stack_max.cpp
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73 lines (65 loc) · 987 Bytes
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#include <iostream>
#include <stack>
#include <vector>
struct MaxStack
{
void pushv(int val) {
values.push(val);
if (maxv.empty())
maxv.push(val);
else
maxv.push(std::max(maxv.top(), val));
}
void popv() {
if (!values.empty() && !maxv.empty())
{
values.pop();
maxv.pop();
}
}
int max() {
if (!maxv.empty())
return maxv.top();
else
return -1;
}
private:
std::stack<int> values;
std::stack<int> maxv;
};
void read_commands(int n)
{
std::string command;
int val;
MaxStack st;
int ret;
std::vector<int> log;
while (n != 0)
{
std::cin >> command;
if (command == "max")
{
ret = st.max();
if (ret >= 0)
log.push_back(ret);
}
else if (command == "pop")
st.popv();
else if (command == "push")
{
std::cin >> val;
st.pushv(val);
}
--n;
}
for (int i = 0; i < log.size(); ++i)
std::cout << log[i] << std::endl;
}
int main(void)
{
int n = 0;
std::cin >> n;
if (n)
read_commands(n);
return 0;
}