python/C++专题课程/广度优先搜索/Bfs.cpp

#include <bits/stdc++.h>

using namespace std;

int a[11][11] =
        {
                {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}
        };
int dir[4][2] = {{-1, 0},
                 {0,  1},
                 {1,  0},
                 {0,  -1}};
int vis[11][11];//用来标记有没有走过（有没有在队列中)
int b[11][11];//用来记录bfs的过程
struct Node {
    int x, y;
};
queue<Node> q;

int main() {
    memset(b, 0, sizeof(b));
    memset(vis, 0, sizeof(vis));
    while (!q.empty()) q.pop();//初始化队列

    Node start;
    start.x = 1;
    start.y = 1;
    vis[1][1] = 1;
    b[1][1] = 1;
    q.push(start);//把起点放进队列
    bool f = 0;
    while (!q.empty()) {
        Node temp;
        temp = q.front();//取出队头元素
        q.pop();
        int x = temp.x;
        int y = temp.y;
        if (x == 8 && y == 8)//若走到了
        {
            f = 1;
            Node road[111];//用来记录路径
            //for(int i=1;i<=8;i++)//可以通过输出b数组来观察bfs的实现过程
            //{
            //    for(int j=1;j<=8;j++)
            //    {
            //        printf("%5d",b[i][j]);
            //    }
            //    cout<<endl;
            //}
            //cout<<b[8][8]<<endl;
            int k = 1;
            while (!(x == 1 && y == 1))//通过b数组来找到之前是哪一个点走到x，y的
            {
                road[k].x = x;
                road[k++].y = y;
                for (int i = 0; i < 4; i++) {
                    int xx = x + dir[i][0];
                    int yy = y + dir[i][1];
                    if (xx < 1 || yy < 1 || xx > 8 || yy > 8) continue;//超出范围的不要
                    if (b[xx][yy] == b[x][y] - 1) {
                        x = xx;//倒退回去
                        y = yy;
                        break;//一定要跳出，要把更新的x，y放到road里
                    }
                }
            }
            road[k].x = 1;//别忘了把起点放进去
            road[k].y = 1;
            for (int i = k; i >= 1; i--)//输出路径
            {
                cout << road[i].x << " " << road[i].y << endl;
            }
        }
        if (f == 1) //找到路了就不用再跑大循环了
            break;

        for (int i = 0; i < 4; i++)//遍历四个方向
        {
            int xx = x + dir[i][0];
            int yy = y + dir[i][1];
            if (a[xx][yy] == 0 && vis[xx][yy] == 0) {
                vis[xx][yy] = 1;
                Node New;
                New.x = xx;
                New.y = yy;
                b[xx][yy] = b[x][y] + 1;//用来标记走到（xx，yy）是第几步
                q.push(New);//放进队列
            }
        }
    }
    return 0;
}