煎饼

一共输入s+1行。

第一行输入三个整数n,m,s，表示煎锅一共有n个位置，煎饼有m种类型，牛牛一共执行s次操作。

第二行到第s+1行每行2-3个整数，具体操作见题目描述。

C++ 解法, 执行用时: 467ms, 内存消耗: 40596K, 提交时间: 2022-06-18 19:57:13

#include "bits/stdc++.h"
 
using namespace std;
 
const int MAXN  = 1e6 + 6;
 
struct node {
    bool flag;
    list<int>cake;
}a[MAXN];
 
int main(void) {
//	freopen("t2_10.in","r",stdin);
//	freopen("t2_10.out","w",stdout);
    int n, m, s;
    cin >> n >> m >> s;
    for (int i = 0; i < s; ++i) {
        int key, x;
        scanf("%d %d", &key, &x);
        if (key == 1) {
            int k; scanf("%d", &k);
            a[x].cake.push_back(k);
        }else if (key == 2) {
            int y;
            scanf("%d", &y);
            //cout << "merge y to x before: "; for (auto it : a[x].cake) cout << it << ' '; cout << endl;
            if (a[y].flag && a[x].flag) {
                a[x].cake.merge(a[y].cake, greater<int>());
            }else if (!a[y].flag && !a[x].flag) {
                a[x].cake.merge(a[y].cake);
            }else if (!a[y].flag && a[x].flag) {
                while (!a[y].cake.empty()) {
                    a[x].cake.push_front(a[y].cake.back());
                    a[y].cake.pop_back();
                }
            }else {
                while (!a[y].cake.empty()) {
                    a[x].cake.push_back(a[y].cake.back());
                    a[y].cake.pop_back();
                }
            }
            //cout << "merge end: "; for (auto it : a[x].cake) cout << it << ' '; cout << endl;
            a[y].cake.clear();
            a[y].flag = false;
        }else if (key == 3) {
            a[key].flag = !a[key].flag;
        }else {
            if (a[x].cake.empty()) {
                printf("-1\n");
            }else if (a[x].flag) {
                printf("%d\n", a[x].cake.front());
                //a[key].cake.pop_front();
            }else {
                printf("%d\n", a[x].cake.back());
                //a[key].cake.pop_back();
            }
        }
    }
    //for (int i = 0; i <= n; ++i) { cout << i << ": "; for (auto it : a[i].cake) cout << it << ' '; cout << endl;}
 
    return 0;
}

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