最短路dijkstra

using namespace std;

const int INF = INT_MAX;
//结构体node，有自己的坐标，还有一个距离？
struct Node {
    int x, y, distance;
    bool operator>(const Node& other) const {
        return distance > other.distance;
    }
};

int dijkstra(const vector<vector<int>>& grid, const pair<int, int>& start, const pair<int, int>& end) {
    //获取n
    int n = grid.size();
    //创建了一个distance数组
    vector<vector<int>> distance(n, vector<int>(n, INF));
    //优先队列储存node，数据结构为vector<Node>,以小顶堆的方式
    priority_queue<Node, vector<Node>, greater<Node>> pq;
    //放入起点
    pq.push({ start.first, start.second, 0 });
    distance[start.first][start.second] = 0;

    while (!pq.empty()) {
        Node current = pq.top();
        pq.pop();
        //如果到达目的地了，就返回距离
        if (current.x == end.first && current.y == end.second) {
            return current.distance;
        }
        //方向
        int dx[] = { -1, 1, 0, 0 };
        int dy[] = { 0, 0, -1, 1 };
        //生成四个方向
        for (int i = 0; i < 4; i++) {
            //下一个方向的坐标
            int nx = current.x + dx[i];
            int ny = current.y + dy[i];
            //没出界
            if (nx >= 0 && nx < n && ny >= 0 && ny < n) {
                //grid存的是值，newDistance
                int newDistance = current.distance + grid[nx][ny];
                //处理其它三个方向的坐标，如果其它三个方向的坐标小于这个distance
                if (newDistance < distance[nx][ny]) {
                    distance[nx][ny] = newDistance;
                    pq.push({ nx, ny, newDistance });
                }
            }
        }
    }

    return -1; // Should not reach here if a valid path exists
}

int main() {
    int t;
    cin >> t;
    //循环次数
    while (t--) {
        //几阶矩阵
        int n;
        cin >> n;
        //地图
        vector<vector<int>> grid(n, vector<int>(n));
        //起始坐标和终点坐标
        pair<int, int> start, end;
        //输入地图
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                cin >> grid[i][j];

                if (grid[i][j] == 0) {
                    if (start.first == 0 && start.second == 0) {
                        start = { i, j };
                    }
                    else {
                        end = { i, j };
                    }
                }
            }
        }
        //传入了地图，起始坐标，终点坐标
        int result = dijkstra(grid, start, end);
        cout << result << endl;
    }

    return 0;
}