SOJ 1150.简单魔板

题目大意：中文题面，可直接看题目理解。

数据结构：

MagicPlate:

　　int up : 代表魔板上层的状态

　　int down : 代表魔板下层的状态

　　char op : 表示当前魔板状态是通过哪种操作('A'、'B'、'C')获得的

　　int pre : 代表通过op操作获得当前魔板状态的魔板状态（也即父节点）

vector<MagicPlate> vt : 模拟队列

解题思路：通过广搜对三叉树进行遍历。若发现重复状态，适当剪枝以降低复杂度。

代码如下：

#include <iostream>
#include <vector>
#include <string>
using namespace std;

class MagicPlate {
public:
    void setUp(int u) {
        up = u;
    }

    void setDown(int d) {
        down = d;
    }

    bool stateEqual(const MagicPlate & mp) {
        return up == mp.up && down == mp.down;
    }

    void reset() {
        up = 1234;
        down = 8765;
        op = NULL;
        pre = -1;
    }

    void operateA() {
        int temp = up;
        up = down;
        down = temp;

        op = 'A';
    }

    void operateB() {
        up = up / 10 + up % 10 * 1000;
        down = down / 10 + down % 10 * 1000;

        op = 'B';
    }

    void operateC() {
        int u = up % 1000 / 10;
        int u1 = u / 10;
        int u2 = u % 10;
        int d = down % 1000 / 10;
        int d1 = d / 10;
        int d2 = d % 10;
        
        up = up / 1000 * 1000 + d1 * 100 + u1 * 10 + up % 10;
        down = down / 1000 * 1000 + d2 * 100 + u2 * 10 + down % 10;

        op = 'C';
    }

    void setPre(int p) {
        pre = p;
    }

    int getPre() {
        return pre;
    }
    
    char getOp() {
        return op;
    }

private:
    int up;
    int down;
    char op;
    int pre;
};

vector<MagicPlate> vt;
string opStr;
int fp, rp;
int n;

void init() {
    opStr = "";
    vt.clear();
}

void getGoal(MagicPlate * mp) {
    while (mp->getPre() != -1) {
        opStr.push_back(mp->getOp());
        mp = &vt[mp->getPre()];
    }
}

bool visited(const MagicPlate &mp) {
    //return false;
    for (int i = 0; i <= fp; i++) {
        if (vt[i].stateEqual(mp)) {
            return true;
        }
    }
    return false;
}

int main() {
    while (cin >> n, n != -1) {
        init();
        int temp;
        int up = 0;
        for (int i = 0; i < 4; i++) {
            cin >> temp;
            up = up * 10 + temp;
        }
        int down = 0;
        for (int i = 0; i < 4; i++) {
            cin >> temp;
            down = down * 10 + temp;
        }
        MagicPlate targetMP;
        targetMP.setUp(up);
        targetMP.setDown(down);

        MagicPlate begin;
        begin.reset();
        vt.push_back(begin);
        fp = 0;
        rp = 1;

        if (targetMP.stateEqual(begin)) {
            cout << 0 << endl;
            continue;
        }

        bool flag = false;
        int step;
        for (step = 1; step <= n; step++) {
            int trp = rp;
            while (fp < trp) {
                MagicPlate mp = vt[fp];
                MagicPlate mpA(mp);
                mpA.operateA();
                mpA.setPre(fp);
                if (mpA.stateEqual(targetMP)) {
                    getGoal(&mpA);
                    flag = true;
                    break;
                } else if (!visited(mpA)) {
                    vt.push_back(mpA);
                    rp++;
                }

                MagicPlate mpB(mp);
                mpB.operateB();
                mpB.setPre(fp);
                if (mpB.stateEqual(targetMP)) {
                    getGoal(&mpB);
                    flag = true;
                    break;
                } else if (!visited(mpB)) {
                    vt.push_back(mpB);
                    rp++;
                }

                MagicPlate mpC(mp);
                mpC.operateC();
                mpC.setPre(fp);
                if (mpC.stateEqual(targetMP)) {
                    getGoal(&mpC);
                    flag = true;
                    break;
                } else if (!visited(mpC)) {
                    vt.push_back(mpC);
                    rp++;
                }

                fp++;
            }
            if (flag) break;
        }

        if (flag) {
            cout << step << " " << string(opStr.rbegin(), opStr.rend()) << endl;
        } else {
            cout << -1 << endl;
        }
    }
}