Question

我正在尝试通过给定的活动网络找到所有路径，并认为我可以使用递归来完成。这很像遍历具有不同文件夹和子文件夹的网络驱动器。

我已经定义了一个活动类（用于存储每个活动的属性）和一个网络类（用于存储网络的活动）。我将网络对象作为参数传递给递归函数调用。递归函数不能按预期工作。它给出了分段错误，似乎无法正确访问网络对象。

有人能指出我如何解决这个问题的正确方向（以及如何将找到的路径存储在二维数组中）。

以下是代码：

#include <iostream>

using namespace std;

class Activity {
   public:
      int id;
      double duration;
      int successors[10];
};

class Network {
   public:
      Activity activities[];
};

int traverse(int, Network);

int main()
{
    // define the set of successors for each activity
    // a value of -1 indicates that no more successors are present
    const int successorset[][5] = {
        { 1,2,3,-1 },
        { 5,-1 },
        { 4,-1 },
        { 4,-1 },
        { 5,-1 },
        { -1},
        };

    // two dimensional array where for each path the activity ids are stored
    int pathset [10][10];

    // declare activities
    Activity Activity0, Activity1, Activity2, Activity3, Activity4, Activity5;

    // declare network
    Network NetworkMain;

    // define activity 0
    Activity0.id = 0;
    Activity0.duration = 0;
    Activity0.successors[0] = successorset[0][0];
    Activity0.successors[1] = successorset[0][1];
    Activity0.successors[2] = successorset[0][2];
    Activity0.successors[3] = successorset[0][3];
    NetworkMain.activities[0] = Activity0;

    // define activity 1
    Activity1.id = 1;
    Activity1.duration = 3;
    Activity1.successors[0] = successorset[1][0];
    Activity1.successors[1] = successorset[1][1];
    NetworkMain.activities[1] = Activity1;

    // define activity 2
    Activity2.id = 2;
    Activity2.duration = 1;
    Activity2.successors[0] = successorset[2][0];
    Activity2.successors[1] = successorset[2][1];
    NetworkMain.activities[2] = Activity2;

    // define activity 3
    Activity3.id = 3;
    Activity3.duration = 2;
    Activity3.successors[0] = successorset[3][0];
    Activity3.successors[1] = successorset[3][1];
    NetworkMain.activities[3] = Activity3;

    // define activity 4
    Activity4.id = 4;
    Activity4.duration = 4;
    Activity4.successors[0] = successorset[4][0];
    Activity4.successors[1] = successorset[4][1];
    NetworkMain.activities[4] = Activity4;

    // define activity 5
    Activity5.id = 5;
    Activity5.duration = 0;
    Activity5.successors[0] = successorset[5][0];
    NetworkMain.activities[5] = Activity5;

    // print info on all activities to check whether they are defined correctly
    for( int a = 0; a < 6; a++ ) {
        cout << "id of activity = " << NetworkMain.activities[a].id << endl;
        cout << "duration of activity = " << NetworkMain.activities[a].duration << endl;
        int s = 0;
        while (NetworkMain.activities[a].successors[s]!=-1) {
            cout << "successor of activity " << a << " = " << NetworkMain.activities[a].successors[s] << endl;
            s++;
        }
    }

    // call recursive function to traverse through all paths of the network
    traverse(0, NetworkMain);

    return 0;
}

int traverse(int id, Network net)
{
    if (net.activities[id].successors[0]==-1) // reached finish activity
    {
        cout << "reached finish " << endl;
        return 1;
    }
    else
    {
        cout << "id of activity under investigation " << net.activities[id].id << endl;
        int t = 0;
        while (net.activities[id].successors[t]!=-1) {
            cout << "going to investigate successor " << t << endl;
            traverse(net.activities[id].successors[t], net);
            t++;
        }
    }
}

这是输出：

id of activity = 0
duration of activity = 0
successor of activity 0 = 1
successor of activity 0 = 2
successor of activity 0 = 3
id of activity = 1
duration of activity = 3
successor of activity 1 = 5
id of activity = 2
duration of activity = 1
successor of activity 2 = 4
id of activity = 3
duration of activity = 2
successor of activity 3 = 4
id of activity = 4
duration of activity = 4
successor of activity 4 = 5
id of activity = 5
duration of activity = 0
id of activity under investigation -578861888
going to investigate successor 0
id of activity under investigation 0
going to investigate successor 0
id of activity under investigation -581127744
going to investigate successor 0
Segmentation fault (core dumped)

Process returned 139 (0x8B)   execution time : 0.087 s
Press ENTER to continue.

编辑：应该添加新手警报，下面是调试器输出。

Active debugger config: GDB/CDB debugger:Default
Building to ensure sources are up-to-date
Selecting target: 
Debug
Adding source dir: /home/home/Desktop/recursion/
Adding source dir: /home/home/Desktop/recursion/
Adding file: /home/home/Desktop/recursion/bin/Debug/recursion
Changing directory to: /home/home/Desktop/recursion/.
Set variable: LD_LIBRARY_PATH=.:

[debug]Command-line: /usr/bin/gdb -nx -fullname -quiet  -args /home/home/Desktop/recursion/bin/Debug/recursion
[debug]Working dir : /home/home/Desktop/recursion

Starting debugger: /usr/bin/gdb -nx -fullname -quiet  -args /home/home/Desktop/recursion/bin/Debug/recursion
done

[debug]Reading symbols from /home/home/Desktop/recursion/bin/Debug/recursion...done.
[debug](gdb) 
[debug]> set prompt >>>>>>cb_gdb:

Registered new type: wxString
Registered new type: STL String
Registered new type: STL Vector
Setting breakpoints

[debug]>>>>>>cb_gdb:
[debug]> show version
[debug]GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.04) 7.11.1
[debug]Copyright (C) 2016 Free Software Foundation, Inc.
[debug]License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
[debug]This is free software: you are free to change and redistribute it.
[debug]There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
[debug]and "show warranty" for details.
[debug]This GDB was configured as "x86_64-linux-gnu".
[debug]Type "show configuration" for configuration details.
[debug]For bug reporting instructions, please see:
[debug]<http://www.gnu.org/software/gdb/bugs/>.
[debug]Find the GDB manual and other documentation resources online at:
[debug]<http://www.gnu.org/software/gdb/documentation/>.
[debug]For help, type "help".
[debug]Type "apropos word" to search for commands related to "word".
[debug]>>>>>>cb_gdb:
[debug]> set confirm off

Debugger name and version: GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.04) 7.11.1

[debug]>>>>>>cb_gdb:
[debug]> set width 0
[debug]>>>>>>cb_gdb:
[debug]> set height 0
[debug]>>>>>>cb_gdb:
[debug]> set breakpoint pending on
[debug]>>>>>>cb_gdb:
[debug]> set print asm-demangle on
[debug]>>>>>>cb_gdb:
[debug]> set unwindonsignal on
[debug]>>>>>>cb_gdb:
[debug]> set print elements 0
[debug]>>>>>>cb_gdb:
[debug]> set disassembly-flavor intel
[debug]>>>>>>cb_gdb:
[debug]> catch throw
[debug]Catchpoint 1 (throw)
[debug]>>>>>>cb_gdb:
[debug]> source /usr/share/codeblocks/scripts/stl-views-1.0.3.gdb
[debug]>>>>>>cb_gdb:
[debug]> directory /home/home/Desktop/recursion/
[debug]Source directories searched: /home/home/Desktop/recursion:$cdir:$cwd
[debug]>>>>>>cb_gdb:
[debug]Using terminal's PID as console PID 13148, TTY /dev/pts/1
[debug]> tty /dev/pts/1
[debug]Queued:[tty /dev/pts/1]
[debug]>>>>>>cb_gdb:
[debug]> run
[debug]Starting program: /home/home/Desktop/recursion/bin/Debug/recursion 
[debug]Program received signal SIGSEGV, Segmentation fault.
[debug]0x0000000000400ee9 in traverse (id=-140179936, net=...) at /home/home/Desktop/recursion/main.cpp:103
[debug]/home/home/Desktop/recursion/main.cpp:103:2808:beg:0x400ee9
[debug]>>>>>>cb_gdb:

Program received signal SIGSEGV, Segmentation fault.
At /home/home/Desktop/recursion/main.cpp:103

[debug]> bt 30
[debug]#0  0x0000000000400ee9 in traverse (id=-140179936, net=...) at /home/home/Desktop/recursion/main.cpp:103
[debug]#1  0x0000000000400ff1 in traverse (id=0, net=...) at /home/home/Desktop/recursion/main.cpp:114
[debug]#2  0x0000000000400ff1 in traverse (id=6, net=...) at /home/home/Desktop/recursion/main.cpp:114
[debug]#3  0x0000000000400ff1 in traverse (id=0, net=...) at /home/home/Desktop/recursion/main.cpp:114
[debug]#4  0x0000000000400e91 in main () at /home/home/Desktop/recursion/main.cpp:96
[debug]>>>>>>cb_gdb:

Answer 1

似乎是一个新手的错误，我不得不声明活动数组的大小，以便在计算机的内存中腾出空间。

不正确：

class Network {
   public:
      Activity activities[];
};

正确：

class Network {
   public:
      Activity activities[6]; // given 6 activities
};

感谢大家的帮助。

用对象作为函数参数

1 个答案: