C/C++ code
#include <stdio.h>
#include <cmath>
#include <iostream> 
#include <fstream>
#include <time.h>
using namespace std; 

const int iAntCount=34;//螞蟻數量 
const int iCityCount=51;//城市數量 
const int iItCount=2000;//最大跌代次數 
const double Q=100; 
const double alpha=1; 
const double beta=5; 
const double rou=0.5; 

int besttour[iCityCount];//最有路徑列表 

double  rnd(int low,double uper)//獲得隨機數 
{ 
    double p=(rand()/(double)RAND_MAX)*((uper)-(low))+(low); 
    return (p); 
}; 
int rnd(int uper) 
{ 
    return (rand()%uper); 
}; 
class GInfo//tsp地圖信息，包含了信息素，城市距離，和信息素變化矩陣 
{ 
public: 
    double m_dDeltTrial[iCityCount][iCityCount]; 
    double m_dTrial[iCityCount][iCityCount]; 
    double distance[iCityCount][iCityCount]; 

}; 
GInfo Map; 
class ant 
{ 
private: 
    int ChooseNextCity();//選擇城市 
    double prob[iCityCount]; 
    int m_iCityCount; 
    int AllowedCity[iCityCount];//沒有走過的城市 
public: 
    void addcity(int city); 
    int tabu[iCityCount]; 
    void Clear(); 
    void UpdateResult(); 
    double m_dLength; 
    double m_dShortest; 
    void move(); 
    ant(); 
    void move2last(); 

}; 
void ant::move2last() 
{ 
    int i; 
    for(i=0;i<iCityCount;i++) 

        if (AllowedCity[i]==1) 
        { 
            addcity(i); 
            break; 
        } 
} 

void ant::Clear() 
{ 
    m_dLength=0; 
    int i; 
    for(i=0; i<iCityCount;i++) 
    { 
        prob[i]=0; 
        AllowedCity[i]=1; 
        i=tabu[iCityCount-1]; 
        m_iCityCount=0; 
        addcity(i); 
    } 
} 
ant::ant() 
{ 
    m_dLength=m_dShortest=0; 
    m_iCityCount=0; 
    int i; 
    for(i=0;i<iCityCount;i++) {

        AllowedCity[i]=1; 
        prob[i]=0; 
    } 
} 
void ant::addcity(int city) 
{ 
    //add city to tabu; 
    tabu[m_iCityCount]=city; 
    m_iCityCount++; 
    AllowedCity[city]=0; 
} 
int ant::ChooseNextCity() 
{ 
    //Update the probability of path selection 
    //select a path from tabu[m_iCityCount-1] to next
    int i; 
    int j=10000; 
    double temp=0; 
    int curCity=tabu[m_iCityCount-1]; 
    for (i=0;i<iCityCount;i++) {

        if((AllowedCity[i]==1)) 
        { 
            temp+=pow((1.0/Map.distance[curCity][i]),beta)*pow((Map.m_dTrial[curCity][i]),alpha); 
        } 
    }
    double sel=0; 
    for (i=0;i<iCityCount;i++) {

        if((AllowedCity[i]==1)) 
        { 
            prob[i]=pow((1.0/Map.distance[curCity][i]),(int)beta)*pow((Map.m_dTrial[curCity][i]),(int)alpha)/temp; 
            sel+=prob[i]; 
        } 
        else 
            prob[i]=0; 
    } 
    double mRate=rnd(0,sel); 
    double mSelect=0; 
    for ( i=0;i<iCityCount;i++) {

        if((AllowedCity[i]==1)) 
            mSelect+=prob[i] ; 
        if (mSelect>=mRate) {j=i;break;} 
    } 
    if (j==10000) 
    { 
        temp=-1; 
        for (i=0;i<iCityCount;i++) {

            if((AllowedCity[i]==1)) 
                if (temp)   { 
                    temp=pow((1.0/Map.distance[curCity][i]),beta)*pow((double)(Map.m_dTrial[curCity][i]),alpha); 
                    j=i; 
                } 
        } 
    } 
    return j; 
} 
void ant::UpdateResult() 
{ 
    // Update the length of tour 
    int i; 
    for(i=0;i<iCityCount-1;i++) 

        m_dLength+=Map.distance[tabu[i]][tabu[i+1]]; 
    m_dLength+=Map.distance[tabu[iCityCount-1]][tabu[0]]; 
} 
void ant::move() 
{ 
    //the ant move to next town and add town ID to tabu. 
    int j; 
    j=ChooseNextCity(); 
    addcity(j); 
} 
class project 
{ 
public: 
    void UpdateTrial(); 
    double m_dLength; 
    void initmap(); 
    ant ants[iAntCount]; 
    void GetAnt(); 
    void StartSearch(); 
    project(); 
}; 
void project::UpdateTrial() 
{ 
    //calculate the changes of trial information 
    int i; 
    int j; 
    for(i=0;i<iAntCount;i++) {
        for (j=0;j<iCityCount-1;j++) 
        {  
            Map.m_dDeltTrial[ants[i].tabu[j]][ants[i].tabu[j+1]]+=Q/ants[i].m_dLength ; 
            Map.m_dDeltTrial[ants[i].tabu[j+1]][ants[i].tabu[j]]+=Q/ants[i].m_dLength; 
        } 
        Map.m_dDeltTrial[ants[i].tabu[iCityCount-1]][ants[i].tabu[0]]+=Q/ants[i].m_dLength; 
        Map.m_dDeltTrial[ants[i].tabu[0]][ants[i].tabu[iCityCount-1]]+=Q/ants[i].m_dLength; 
    } 
    for (i=0;i<iCityCount;i++) {
        for (j=0;j<iCityCount;j++) 
        { 
            Map.m_dTrial[i][j]=(rou*Map.m_dTrial[i][j]+Map.m_dDeltTrial[i][j] ); 
            Map.m_dDeltTrial[i][j]=0; 
        } 
    } 
} 
void project::initmap() 
{ 
    int i; 
    int j; 
    for(i=0;i<iCityCount;i++) 
        for (j=0;j<iCityCount;j++) 
        { 


            Map.m_dTrial[i][j]=1; 
            Map.m_dDeltTrial[i][j]=0; 
        } 
} 
project::project() 
{ 
    //initial map,read map infomation from file . et. 
    initmap(); 
    m_dLength=10e9; 


    ifstream in("eil51.tsp"); 

    struct city 
    { 
        int num; 
        int x; 
        int  y; 
    }cc[iCityCount]; 

    for (int i=0;i<iCityCount;i++) 
    { 
        in>>cc[i].num>>cc[i].x>>cc[i].y; 
        besttour[i]=0; 
    } 
    int j; 
    for(int i=0;i<iCityCount;i++) 
        for (j=0;j<iCityCount;j++) 
        { 
            { 
                Map.distance[i][j]=sqrt(pow((double)(cc[i].x-cc[j].x),2)+pow((double)(cc[i].y-cc[j].y),2)); 
            } 
        } 
} 
void project::GetAnt() 
{ 
    //randomly put ant into map 
    int i=0; 
    int city; 
    srand( (unsigned)time( NULL ) +rand()); 
    for (i=0;i<iAntCount;i++) 
    { 
        city=rnd(iCityCount); 
        ants[i].addcity(city); 
    } 
} 
void project::StartSearch() 
{ 
    //begin to find best solution 
    int max=0;//every ant tours times 
    int i; 
    int j; 
    double temp; 
    int temptour[iCityCount]; 
    while (max<iItCount) 
    {  
        for(j=0;j<iAntCount;j++) 
        { 
            for (i=0;i<iCityCount-1;i++) 
                ants[j].move(); 
        } 
        for(j=0;j<iAntCount;j++) 
        {  ants[j].move2last(); 
        ants[j].UpdateResult (); 
        } 
        //find out the best solution of the step and put it into temp 
        int t; 
        temp=ants[0].m_dLength; 
        for (t=0;t<iCityCount;t++) 
            temptour[t]=ants[0].tabu[t]; 
        for(j=0;j<iAntCount;j++) 
        { 
            if (temp>ants[j].m_dLength) { 
                temp=ants[j].m_dLength; 
                for ( t=0;t<iCityCount;t++) 
                    temptour[t]=ants[j].tabu[t]; 
            } 
        }
        if(temp<m_dLength){ 
            m_dLength=temp; 
            for ( t=0;t<iCityCount;t++) 
                besttour[t]=temptour[t]; 
        } 
        printf("%d : %f\n",max,m_dLength); 
        UpdateTrial(); 
        for(j=0;j<iAntCount;j++) 
            ants[j].Clear(); 
        max++; 
    } 
    printf("The shortest toure is : %f\n",m_dLength); 
    for ( int t=0;t<iCityCount;t++) 
        printf(" %d ",besttour[t]); 
} 
int main() 
{ 
    project TSP; 
    TSP.GetAnt(); 
    TSP.StartSearch(); 
    return 0; 
}