bfs求最短路径

经典迷宫问题

AC代码

#include <iostream>
#include <cstring>
#include <algorithm>
#include <queue>

using namespace std;
const int N = 110;
int n, m;
int g[N][N], d[N][N];
typedef pair<int, int> PII;
queue<PII> q;
int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};//四个方向向量

int bfs()
{
    memset(d, -1, sizeof(d));
    q.push({0, 0});
    d[0][0] = 0;
    
    while(q.size())
    {
        auto t = q.front();
        q.pop();
        
        for(int i = 0; i < 4; i++)
        {
            int x = t.first + dx[i];
            int y = t.second + dy[i];
            if(x >= 0 && x < n && y >= 0 && y < m && g[x][y] == 0 && d[x][y] == -1)
            {
                d[x][y] = d[t.first][t.second] + 1;
                q.push({x, y});
            }
        }
    }
    
    return d[n - 1][m - 1];
}

int main()
{
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    cin >> n >> m;
    for(int i = 0; i < n; i++)
    {
        for(int j = 0; j < m; j++)
        {
            cin >> g[i][j];
        }
    }
    cout << bfs() << endl;
    return 0;
}

水桶传递队列

AC代码：

#include <iostream>
#include <cstring>
#include <algorithm>
#include <queue>

using namespace std;
char g[10][10];
int d[10][10];
typedef pair<int, int> PII;
queue<PII> q;
int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};

void bfs(int x, int y)
{
    memset(d, -1, sizeof d);
    q.push({x, y});
    d[x][y] = 0;
    
    while(q.size())
    {
        auto t = q.front();
        q.pop();
        
        for(int i = 0; i < 4; i++)
        {
            int m = t.first + dx[i], n = t.second + dy[i];
            
            if(m >= 0 && m < 10 && n >= 0 && n < 10 && d[m][n] == -1 && g[m][n] == '.')
            {
                q.push({m, n});
                d[m][n] = d[t.first][t.second] + 1;
            }
            else if(m >= 0 && m < 10 && n >= 0 && n < 10 && d[m][n] == -1 && g[m][n] == 'L')
            {
                d[m][n] = d[t.first][t.second] + 1;
                cout << d[m][n] - 1 << endl;
            }
        }
    }

}

int main()
{
    int x1, y1, x2, y2;
    for(int i = 0; i < 10; i++)
        for(int j = 0; j < 10; j++)
        {
            cin >> g[i][j];
            if(g[i][j] == 'B') x1 = i, y1 = j;
            else if(g[i][j] == 'L') x2 = i, y2 = j;
        }

    bfs(x1, y1);
    return 0;
}