[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。