[Luogu 3952] NOIP2017 时间复杂度

[Luogu 3952] NOIP2017 时间复杂度

<题目链接>

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一年的时间说长不长，说短，也不短。

一年之内无数次觉得难得可怕的题目，原来也就模拟这么回事儿。

#include <cstdio>
#include <iostream>
#include <set>
#include <stack>
#include <string>

int T; 

struct Layer
{
    std::string name;
    int state;
    Layer(std::string name, int state): name(name), state(state){}
}; 

int Solve(std::string s)
{
    if(s == "O(1)")
        return 0;
    int ans = 0;
    for(int i = 4; s[i] != ')'; ++i)
        ans = ans * 10 + s[i] - '0';
    return ans;
}

int Number(std::string s)
{
    if(s[0] == 'n')
        return 0;
    int ans = 0;
    for(int i = 0; s[i]; ++i)
        ans = ans * 10 + s[i] - '0';
    return ans;
}

int main(void)
{
    scanf("%d", &T);
    while(T--)
    {
        bool right = true;
        int n, ans, cur = 0, fact = 0;
        std::set<std::string> Name;
        std::stack<Layer> S;
        std::string a[5];
        scanf("%d", &n);
        std::cin >> a[0];
        ans = Solve(a[0]);
        for(int i = 1; i <= n; ++i)
        {
            std::cin >> a[1];
            if(a[1] == "F")
            {
                for(int i = 2; i <= 4; ++i)
                    std::cin >> a[i];
                if(right && !Name.count(a[2]))
                {
                    int state, x = Number(a[3]), y = Number(a[4]);
                    if((!S.empty() && S.top().state == -1) || (!x && y) || (x > y && y))
                        state = -1;
                    else if(x && !y)
                    {
                        state = 1;
                        ++cur;
                    }
                    else
                        state = 0;
                    Name.insert(a[2]);
                    S.push(Layer(a[2], state));
                }
                else
                    right = false;
            }
            else if(right)
            {
                if(!S.empty())
                {
                    Layer t = S.top();
                    Name.erase(t.name);
                    S.pop();
                    fact = std::max(fact, cur);
                    if(t.state == 1)
                        --cur;
                }
                else
                    right = false;
            }
        }
        if(!S.empty())
            right = false;
        if(!right)
            puts("ERR");
        else
            puts(ans == fact ? "Yes" : "No");
    }
    return 0;
}

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谢谢阅读。