模拟退火求解TSP问题<2变换法产生路径>

<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">模拟退火解TSP</span>

<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);"></span><pre name="code" class="cpp">/*
 * @file					SA.cpp
 * @brief				SA解TSP
 * @author/Univ.			taoxiaoxiao/XMU
 * @date				11-2-2014
*/

#include <iostream>
#include <fstream>
#include <random>
using namespace std;

#define max 51					//最大的输入规格
int a[max][max];				//距离矩阵
int curPath[max], newPath[max], bestPath[max];  //当前解、新解、最优解
int length, bestLength = 0;			//解的结果、最优解的结果
int n;						//输入的节点数
int Lk= 2000;					//Mapkob链长
double t = 100.0, alpha = 0.9;			//温度、衰减速度

double rand1()
{
	//产生0-1间随机数

	static default_random_engine e;			//引擎
	static uniform_real_distribution<double> u(0, 1);	//分布

	return u(e);
}

int rand2(int n)
{
	static default_random_engine e;			//引擎
	static uniform_int_distribution<int> u(1, n);		//分布
	return u(e);
}

inline void swap(int &a, int &b)
{
	int tmp = a;
	a = b;
	b = tmp;
}

int getLength(int *p)
{
	int len = 0;
	for (int i = 1; i <= n - 1; ++i)
	{
		len += a[p[i]][p[i + 1]];
	}
	len += a[p[n]][p[1]];

	return len;
}

/*2变换法产生新路径*/
int getNewPath()
{
	//获得新路径，并求出新长度
	int k, m;
	int newLen = 0;

	/* 2分交换 */
	while (1)
	{
		k = rand2(n);
		m = rand2(n);
		if (k != m)
			break;
	}
	/* 新路径 */
	swap(newPath[k], newPath[m]);
	newLen = getLength(newPath);

	return newLen;
}

void sa()
{
	int i, count;
	int newLength, delta;
	int s = 0;
	int bChange = 0;

	/*初始化操作*/
	for (i = 1; i<= n; i++)
	{
		bestPath[i]=newPath[i]=curPath[i] = i;
	}
	length = getLength(curPath);
	bestLength = length;

	/*按Metropolis接受准则进行迭代*/
	while (1)
	{
		count = 0;
		//对每个温度tk产生Lk个解 Lk个解构成一个mapkob链
		while (1)
		{
			newLength = getNewPath();
			delta = newLength - length;
			if (delta <= 0 || (delta>0 && exp(-delta / t)>rand1()))
			{
				//是否接受新解
				bChange = 1;
				for (i = 1; i <= n; i++)
				{
					curPath[i] = newPath[i];
				}
				length = newLength;
				if (length < bestLength)
				{
					bestLength = length;
					for (i = 1; i <= n; i++)
					{
						bestPath[i] = curPath[i];
					}
				}
			}
			if (++count >= Lk)
				break;
		}//1-while

		t = alpha * t;			//降温
		if (1==bChange)
		{
			s = 0;
			bChange = 0;
		}
		else
		{
			s++;
		}
		if (s == 2 || t <=1e-6)
		{
			//停止准则
			//温度接近零或者有两次结果没变化时
			break;
		}
	}//2-while
}

int main()
{
	ifstream infile("file2.txt");

	int i, j;
	if (infile.is_open())
		cout << "open file successful." << endl;
	else
	{
		cout << "open file error." << endl;
		return 0;
	}
	while (!infile.eof())
	{
		infile >> n;
		for (i = 1; i <= n; ++i)
		{
			for (j =1; j <= n; ++j)
				infile >> a[i][j];
		}
	}
	infile.close();

	sa();
	for (i = 1; i <= n; ++i)
		cout << bestPath[i] << "->";
	cout << bestPath[1] << endl;
	cout << bestLength << endl;
	system("pause");

	return 0;
}

file2.txt

运行结果