队列的应用——求解迷宫问题

代码示例：

#include <iostream>using namespace std;const int MaxSize = 20;//迷宫最大行、列数const int QueueSize = 100;//顺序队大小struct Box//方块结构体类型{int i;//方块的行号int j;//方块的列号int pre;//本路径中上一方块在队列中的下标};class Queue//非循环顺序队列类{Box *data;//存放队中方块int front, rear;//队头队尾指针public:Queue();//构造函数:队列初始化~Queue();//析构函数:释放队列空间bool QueueEmpty();//判断队列是否为空void edQueue(int x, int y, int pre1);//进队一个方块void deQueue(int &x, int &y, int &cfront);//出队一个方块void DispBox(int cfront);//从cfront出发找一条迷宫路径void DispQueue();//用于输出队中所有元素,调试用};Queue::Queue()//构造函数:队列初始化{data = new Box[QueueSize];front = rear = -1;}Queue::~Queue()//析构函数:释放队列空间{delete[] data;}bool Queue::QueueEmpty()//判断队列是否为空{return(front == rear);}void Queue::edQueue(int x, int y, int pre1)//进队一个方块{rear++;data[rear].i = x;data[rear].j = y; data[rear].pre = pre1;}void Queue::deQueue(int &x, int &y, int &cfront)//出队一个方块{front++;x = data[front].i; y = data[front].j;cfront = front;}void Queue::DispBox(int cfront)//从cfront出发找一条迷宫路径{Box path[QueueSize];int k, d = -1;k = cfront;while (k != -1)//找到入口为止{d++;//将一个方块保存到path中path[d].i = data[k].i; path[d].j = data[k].j;k = data[k].pre;//回退找上一个方块}cout << "一条迷宫路径如下:\n";for (k = d; k >= 0; k--)//反向输出构成一条正向的迷宫路径{cout << "  (" << path[k].i << "," << path[k].j << ")";if ((d - k + 1) % 5 == 0) cout << endl;//每行输出5个方块}cout << endl;}void Queue::DispQueue()//用于输出队中所有元素,调试用{int i;cout << "队中所有元素:\n";for (i = 0; i <= rear; i++)cout << "  " << i << " (" << data[i].i << "," << data[i].j << ")  " << data[i].pre << endl;}class Maze2//用队列求解一条迷宫路径类{int a[MaxSize][MaxSize];//迷宫数组int m, n;//迷宫行列数public:void Seta(int mg[][MaxSize], int m1, int n1);//设置迷宫数组bool mgpath(int xi, int yi, int xe, int ye);};void Maze2::Seta(int mg[][MaxSize], int m1, int n1)//设置迷宫数组{int i, j;m = m1;n = n1;for (i = 0; i<m; i++)for (j = 0; j<n; j++)a[i][j] = mg[i][j];}bool Maze2::mgpath(int xi, int yi, int xe, int ye){int i, j, di, cfront, i1, j1;Queue qu;//创建一个空队ququ.edQueue(xi, yi, -1);//入口进队,其pre置为-1a[xi][yi] = -1;//为避免来回找相邻方块,将进队的方块置为-1while (!qu.QueueEmpty())//队不空时循环{qu.deQueue(i, j, cfront);//出队一个方块,该方块仍在队列中if (i == xe && j == ye)//找到了出口,输出路径{qu.DispBox(cfront);qu.DispQueue();return true;//找到一条路径时返回true}for (di = 0; di<4; di++)//循环扫描每个方位,把每个可走的方块进队{switch (di){case 0:i1 = i - 1; j1 = j;   break;case 1:i1 = i;   j1 = j + 1; break;case 2:i1 = i + 1; j1 = j;   break;case 3:i1 = i;   j1 = j - 1; break;}if (a[i1][j1] == 0)//找到一个相邻可走方块{qu.edQueue(i1, j1, cfront);//将该相邻方块进队,并置其pre为父方块下标cfronta[i1][j1] = -1;//为避免来回找相邻方块,将进队的方块置为-1}}}return false;//未找到任何路径时返回false}void main(){int mg[][MaxSize] = { { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 }, { 1, 0, 0, 1, 0, 0, 0, 1, 0, 1 },{ 1, 0, 0, 1, 0, 0, 0, 1, 0, 1 }, { 1, 0, 0, 0, 0, 1, 1, 0, 0, 1 },{ 1, 0, 1, 1, 1, 0, 0, 0, 0, 1 }, { 1, 0, 0, 0, 1, 0, 0, 0, 0, 1 },{ 1, 0, 1, 0, 0, 0, 1, 0, 0, 1 }, { 1, 0, 1, 1, 1, 0, 1, 1, 0, 1 },{ 1, 1, 0, 0, 0, 0, 0, 0, 0, 1 }, { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 } };Maze2 mz;//创建一个Maze2对象mzmz.Seta(mg, 10, 10);//设置迷宫数组cout << "求(1,1)到(8,8)的迷宫路径\n";if (!mz.mgpath(1, 1, 8, 8))//求入口为(1,1)出口为(8,8)的迷宫路径cout << "不存在迷宫路径\n";}