1057. Stack (30)

/*to solve the problem ,i think we can use stack to maintain the numbers,
and list to keep it sorted,which is very important to find the Median number.
*/
#include<stack>
#include<iostream>
#include<string>
#include<vector>
#include<list>
#include<algorithm>
using namespace std;

int main()
{
    int n;
    stack<int> stak;
    string command;
    int a;
    cin>>n;
    while (n--)
    {
        cin>>command;
        if (command == "Push")
        {
            cin>>a;
            stak.push(a);
        }
        if (command == "Pop")
        {
            if (stak.empty())
            {
                cout<<"Invalid"<<endl;
            }
            else
            {
                cout<<stak.top()<<endl;
                stak.pop();
            }
        }
        if (command == "PeekMedian")
        {
            if (stak.empty())
            {
                cout<<"Invalid"<<endl;
                continue;
            }
            vector<int> ls;
            while (!stak.empty())
            {
                ls.push_back(stak.top());
                stak.pop();
            }
            //use the unsorted vector to push_back the stack
            for (int i = ls.size()-1; i >=0 ; i—)
            {
                stak.push(ls[i]);
            }
            sort(ls.begin(),ls.end());
            cout<<ls[ls.size()%2 == 0 ? ls.size()/2-1:(ls.size()+1)/2-1]<<endl;
        }
    }
}

#include <iostream>
#include <set>
#include <algorithm>
#include <stack>
#include <cstring>

using namespace std;

multiset<int> small, big;
stack<int> s;
int mid;

void adjust()
{
    if (small.size() > big.size() + 1)
    {
        auto it = small.end();
        --it;
        big.insert(*it);
        small.erase(it);
    }
    else if (small.size() < big.size())
    {
        auto it = big.begin();
        small.insert(*it);
        big.erase(it);
    }
    if (s.size() > 0)
    {
        auto it = small.end();
        --it;
        mid = *it;
    }
}

int main()
{
    int n;
    char op[15];
    int top, Key;
    scanf("%d", &n);
    while (n--)
    {
        scanf("%s", op);
        if (op[1] == ‘o‘)
        {
            if (s.size() == 0)
                printf("Invalid\n");
            else
            {
                top = s.top();
                s.pop();
                printf("%d\n", top);
                if (mid >= top)
                {
                    auto it = small.find(top);
                    small.erase(it);
                }
                else
                {
                    auto it = big.find(top);
                    big.erase(it);
                }
                adjust();
            }
        }
        else if (op[1] == ‘u‘)
        {
            scanf("%d", &Key);
            if (s.size() == 0)
            {
                small.insert(Key);
                mid = Key;
            }
            else if (Key <= mid)
                small.insert(Key);
            else
                big.insert(Key);
            s.push(Key);
            adjust();
        }
        else if (op[1] == ‘e‘)
        {
            if (s.size() == 0)
                printf("Invalid\n");
            else
                printf("%d\n", mid);
        }
    }
}