C++ code for ant colony optimization algorithm

Question

1.00/5 (1 vote)

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to find shortest path among a number of nodes

What I have tried:

#include <iostream>

using namespace std;
#define INT_MAX  999999

int n=4;
int dp[16][4];
int dist[10][10]={
    {0,20,42,25},
    {20,0,20,34},
    {42,30,0,10},
    {25,34,10,0},
};
int VISITED_ALL=(1<<n)-1;

int tsp(int mask,int pos){
   if(mask==VISITED_ALL){
     return dist[pos][0];
 }
   if(dp[mask][pos]!=-1)
 {
     return dp[mask][pos];
 }
    int ans=INT_MAX;
      for(int city=0;city<n;city++)
      {
        if(mask&(1<<city)==0)
     {
         int newAns=dist[pos][city]+tsp(mask|(1<<city),city);
         ans=min(ans,newAns);
     }
 }
 return dp[mask][pos]=ans;
}
int min (int a, int b)
{
    int p,q;
    
    if(p<q){
     printf("p");
    }
    else{
     printf("q");
    }
}
   
int main()
{
    for(int i=0;i<(1<<n);i++){
        for(int j=0;j<n;j++)
        {
            dp[i][j]=-1;
        }}
        cout<<tsp(1,0)<<endl;
        return 0;
}

this is the code i have tried but it doesn't produce the correct output

Posted 23-Mar-19 20:06pm

Member 14193707

Updated 23-Mar-19 23:21pm

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Patrice T 24-Mar-19 5:13am

Show sample input data, result and expected result.

CPallini 24-Mar-19 5:37am

Could please detail your scenario? As KarstenK pointed out, your code looks featuring several bugs.

2 solutions

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OriginalGriff · Answer 1 · 2019-03-23T20:53:00

Quote:
it doesn't produce the correct output

Tells us nothing about what is going on: it is a useless error report.

Compiling does not mean your code is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:

Input   Expected output    Actual output
  1            2                 1
  2            4                 4
  3            6                 9
  4            8                16

Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:

C#

int Double(int value)
   {
   return value * value;
   }

Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on the first line of the method, and run your app. When it reaches the breakpoint, the debugger will stop, and hand control over to you. You can now run your code line-by-line (called "single stepping") and look at (or even change) variable contents as necessary (heck, you can even change the code and try again if you need to).
Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
Hopefully, that should help you locate which part of that code has a problem, and what the problem is.
This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!

KarstenK · Answer 2 · 2019-03-23T23:21:00

Solution 2

You need to use the debugger. I see some severe bugs in one function.

C++

int min (int a, int b)
{
    //int p,q; not needed
    if(a<b){
     printf("p");
     return a;
    }
    else{
     printf("q");
     return b;
    }
}

And you need to call all code in the main function. So use the debugger!!!

Posted 23-Mar-19 23:21pm

KarstenK

Comments

CPallini 24-Mar-19 5:38am

Indeed. My 5.

Stefan_Lang 25-Mar-19 4:10am

Indeed.

Or just use std::min() rather than reinventing the wheel and ending up with a square...