基于ROS实现A*算法的C++代码示例_ros怎么实现a*代码

以下是基于ROS实现A*算法的C++代码示例：

#include <ros/ros.h>
#include <queue>
#include <vector>
#include <algorithm>
#include <cmath>

struct Node {
    int x, y;
    double f, g, h;
    Node* parent;
    Node(int x, int y) : x(x), y(y), f(0), g(0), h(0), parent(nullptr) {}
};

class AStar {
public:
    AStar(int sx, int sy, int gx, int gy) : start_(new Node(sx, sy)), goal_(new Node(gx, gy)) {
        ROS_ASSERT(sx >= 0 && sy >= 0 && gx >= 0 && gy >= 0);
        ROS_INFO("Start: (%d, %d), Goal: (%d, %d)", sx, sy, gx, gy);
        open_list_.push(start_);
    }

    ~AStar() {
        for (auto& row : nodes_) {
            for (auto node : row) {
                delete node;
            }
        }
    }

    bool plan() {
        while (!open_list_.empty()) {
            auto current = open_list_.top();
            open_list_.pop();
            if (current->x == goal_->x && current->y == goal_->y) {
                ROS_INFO("Found path with cost: %f", current->g);
                path_.push_back(current);
                while (current->parent) {
                    path_.push_back(current->parent);
                    current = current->parent;
                }
                std::reverse(path_.begin(), path_.end());
                return true;
            }
            if (closed_list_.count(current) > 0) {
                continue;
            }
            closed_list_.insert(current);
            expandNode(current);
        }
        ROS_WARN("Failed to find path");
        return false;
    }

    std::vector<Node*> getPath() const {
        return path_;
    }

    void setObstacle(int x, int y) {
        ROS_ASSERT(x >= 0 && y >= 0);
        if (nodes_.size() <= x) {
            nodes_.resize(x + 1);
        }
        if (nodes_[x].size() <= y) {
            nodes_[x].resize(y + 1);
        }
        if (!nodes_[x][y]) {
            nodes_[x][y] = new Node(x, y);
        }
        nodes_[x][y]->g = std::numeric_limits<double>::infinity();
    }

private:
    void expandNode(Node* node) {
        static const std::vector<std::pair<int, int>> dirs = {{-1, 0}, {0, -1}, {1, 0}, {0, 1}};
        for (auto& dir : dirs) {
            int x = node->x + dir.first;
            int y = node->y + dir.second;
            if (x < 0 || y < 0) {
                continue;
            }
            if (x >= nodes_.size() || y >= nodes_[x].size()) {
                continue;
            }
            if (!nodes_[x][y]) {
                nodes_[x][y] = new Node(x, y);
            }
            auto child = nodes_[x][y];
            if (child->g <= node->g + 1) {
                continue;
            }
            child->parent = node;
            child->g = node->g + 1;
            child->h = heuristic(child, goal_);
            child->f = child->g + child->h;
            open_list_.push(child);
        }
    }

    double heuristic(Node* a, Node* b) {
        return std::sqrt(std::pow(a->x - b->x, 2) + std::pow(a->y - b->y, 2));
    }

    Node* start_;
    Node* goal_;
    std::vector<std::vector<Node*>> nodes_;
    std::priority_queue<Node*, std::vector<Node*>, [](Node* a, Node* b) { return a->f > b->f; }> open_list_;
    std::unordered_set<Node*> closed_list_;
    std::vector<Node*> path_;
};

int main(int argc, char** argv) {
    ros::init(argc, argv, "astar");
    ros::NodeHandle nh("~");

    int sx, sy, gx, gy;
    nh.param("start_x", sx, 0);
    nh.param("start_y", sy, 0);
    nh.param("goal_x", gx, 10);
    nh.param("goal_y", gy, 10);

    AStar astar(sx, sy, gx, gy);

    int num_obstacles;
    nh.param("num_obstacles", num_obstacles, 0);
    for (int i = 0; i < num_obstacles; ++i) {
        int x, y;
        nh.getParam("obstacle_" + std::to_string(i) + "_x", x);
        nh.getParam("obstacle_" + std::to_string(i) + "_y", y);
        astar.setObstacle(x, y);
    }

    if (astar.plan()) {
        auto path = astar.getPath();
        for (auto node : path) {
            ROS_INFO("(%d, %d)", node->x, node->y);
        }
    }

    return 0;
}
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在这个例子中，AStar类负责实现A算法，Node结构体表示地图中的一个节点。setObstacle方法用于设置障碍物，plan方法用于执行A算法，getPath方法用于获取计算出的路径。main函数中读取ROS参数，并设置障碍物。运行时，可以使用以下命令启动节点：

rosrun astar astar _start_x:=0 _start_y:=0 _goal_x:=10 _goal_y:=10 _num_obstacles:=2 _obstacle_0_x:=2 _obstacle_0_y:=3 _obstacle_1_x:=4 _obstacle_1_y:=5
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其中，_start_x、_start_y、_goal_x、_goal_y分别表示起点和终点。