使用递归在C++中寻路

Pathfinding in C++ using recursion

本文关键字:寻路 C++ 递归      更新时间:2023-10-16

我正在尝试打印出这个地铁系统中的640条路径。我知道有 640 条路径,因为我已经使用邻接矩阵完成了这个程序。现在我需要用类来做。第一站从"a"开始,路径在车站"l"结束。我在实现递归函数 SearchRoute 时遇到问题,因为我需要打印路径、标记路径,然后再次取消标记路径以允许回溯。目前我只能打印从"a"到"b"的轨道,所以我的递归函数有严重问题。任何建议将不胜感激

页眉

//Function Declarations 
#include <iostream>
#include <string>

using namespace std; 
#ifndef SUBWAY_H
#define SUBWAY_H

class Track
{
    public:
    //Default Constructor 
    Track();
    //Overload Constructor
    Track(char, char);
    //Destructor 
    ~Track();
    //Member variables 
    char node_1;
    char node_2;
    bool visited; 
};

class Station
{
    public:
    //Default Constructor 
    Station();
    //Destructor 
    ~Station();
    //Overload Constructor
    Station(char, int, int);
    //Member variables 
    char station_name; 
    int track_starting_ID;
    int track_size; 
};

class SubwaySystem
{
    public:
    //Default Constructor
    SubwaySystem();
    //Destructor 
    ~SubwaySystem();
    //Recursive function
    void SearchRoute(int);
    //Other member functions 
    friend ostream& operator<<(ostream& os, const Track& my_track);
    friend ostream& operator<<(ostream& os, const Station& my_station);

    //Member variables 
    Track my_track[34];
    Station my_station[12];
    int count_routes; 
    int Current_Station_ID;
    //String to save found route 
};

#endif

.cpp

//Function Definitions
#include <iostream>
#include <string>
#include "subway.h"
using namespace std; 

Track::Track()
{
    visited = 0; 
}

Track::~Track(){
}

Track::Track(char pass_track1, char pass_track2)
{
    node_1 = pass_track1;
    node_2 = pass_track2;
}

Station::Station(){
}

Station::~Station(){
}

Station::Station(char pass_station_name, int pass_start, int pass_size){
    station_name = pass_station_name;
    track_starting_ID = pass_start;
    track_size = pass_size; 
}

SubwaySystem::SubwaySystem()
{
    //Initialize tracks 
    //node_1, node_2
    my_track[0] = Track('a', 'b');
    my_track[1] = Track('b', 'a');
    my_track[2] = Track('b', 'c');
    my_track[3] = Track('b', 'd');
    my_track[4] = Track('b', 'e');
    my_track[5] = Track('b', 'f');
    my_track[6] = Track('c', 'b');
    my_track[7] = Track('c', 'e');
    my_track[8] = Track('d', 'b');
    my_track[9] = Track('d', 'e');
    my_track[10] = Track('e', 'b');
    my_track[11] = Track('e', 'c');
    my_track[12] = Track('e', 'd');
    my_track[13] = Track('e', 'g');
    my_track[14] = Track('e', 'h');
    my_track[15] = Track('f', 'b');
    my_track[16] = Track('f', 'h');
    my_track[17] = Track('g', 'e');
    my_track[18] = Track('g', 'k');
    my_track[19] = Track('h', 'e');
    my_track[20] = Track('h', 'f');
    my_track[21] = Track('h', 'i');
    my_track[22] = Track('h', 'j');
    my_track[23] = Track('h', 'k');
    my_track[24] = Track('i', 'h');
    my_track[25] = Track('i', 'k');
    my_track[26] = Track('j', 'h');
    my_track[27] = Track('j', 'k');
    my_track[28] = Track('k', 'g');
    my_track[29] = Track('k', 'h');
    my_track[30] = Track('k', 'i');
    my_track[31] = Track('k', 'j');
    my_track[32] = Track('k', 'l');
    my_track[33] = Track('l', 'k');
    //Initialize stations 
    //station_name, track_starting_ID, track_size 
    my_station[0] = Station ('a', 0, 1);
    my_station[1] = Station ('b', 1, 5);
    my_station[2] = Station ('c', 6, 2);
    my_station[3] = Station ('d', 8, 2);
    my_station[4] = Station ('e', 10, 5);
    my_station[5] = Station ('f', 15, 2);
    my_station[6] = Station ('g', 17, 2);
    my_station[7] = Station ('h', 19, 5);
    my_station[8] = Station ('i', 24, 2);
    my_station[9] = Station ('j', 26, 2);
    my_station[10] = Station ('k', 28, 5);
    my_station[11] = Station ('l', 33, 1); 
    //Initiaize other members 
    count_routes = 0; 
    Current_Station_ID = 0;
}

SubwaySystem::~SubwaySystem()
{
}

ostream& operator<<(ostream& os, const Track& my_track)
{
    os << my_track.node_1 << '.' << my_track.node_2;
    return os;
}

ostream& operator<<(ostream& os, const Station& my_station)
{
    os << my_station.station_name << '.' << my_station.track_starting_ID << '.' << my_station.track_size;
    return os;
}

void SubwaySystem::SearchRoute(int Current_Station_ID)
{
    while (Current_Station_ID < 33)
    {
        if (Current_Station_ID == 0) //Find a successful route to Station L
        {
            count_routes++; //Add 1 into the variable “count_routes”
            cout << count_routes << " " << my_track[Current_Station_ID] << endl; //Print out this route 
            return; 
        }
        else //Get into recursive Function Body
        {
            for (int i = my_station[Current_Station_ID].track_starting_ID; i < my_station[Current_Station_ID].track_starting_ID + my_station[Current_Station_ID].track_size; i++)
            {
                if (my_track[Current_Station_ID].visited == 0) //if this track is not visited before
                {
                    my_track[Current_Station_ID].visited = 1; //mark this track as visited
                    my_track[Current_Station_ID].node_2 = 1; //mark its corresponding track as visited
                    cout << my_track[Current_Station_ID] << endl; //save this track
                    SearchRoute(Current_Station_ID + 1); //Recursive
                    i--; //Backtrack this track
                    my_track[Current_Station_ID].visited = 0;//mark this track as unvisited
                    my_track[Current_Station_ID].node_2 = 0;//mark its corresponding track as unvisited
                }
            }
        }
    }
}

主要

#include <iostream>
#include <string>
#include "subway.h"
using namespace std; 
int main(int argc, char **argv)
{
    SubwaySystem Test; 
    Test.SearchRoute(0);
}

为什么在

     if (Current_Station_ID == 0) //Find a successful route to Station L
    {
        count_routes++; //Add 1 into the variable “count_routes”
        cout << count_routes << " " << my_track[Current_Station_ID] << endl; //Print out this route 
        return; 
    }

(可能只值得评论,但我讨厌在评论中粘贴代码)

据我所知,您尚未初始化构造函数中的所有成员。至少在赛道上。正确的CTOR如下所示:

Track::Track(char pass_track1, char pass_track2)
{
    node_1 = pass_track1;
    node_2 = pass_track2;
    visited = false;              // this was missing
}

在C++中,您必须初始化所有构造函数中的所有成员。否则,这些值具有内存中以前的值。访问的成员中存在 0 的几率是 1:2^32 =>接近于零。

嗨@ace:就像弗兰克建议的那样,您需要初始化所有变量。 但是,我还将包含一个默认构造函数,该构造函数使单块跟踪并利用重载的构造函数:

Track::Track()    {        Track("~","~");    }
Track::Track(char pass_track1, char pass_track2)
{
    node_1 = pass_track1;
    node_2 = pass_track2;
    visited = false;
}
这意味着基构造函数

将始终从"~"到"~"(可以是任何字符)进行单件跟踪,我还会为基构造函数使用一个字符,该字符在实际使用中不会使用,这样您就可以跟踪和跟踪将来的问题,并且当使用默认构造函数时一目了然, 仅仅因为它包含您选择的所述字符。