算法7.4 旅行商问题的优先队列式分支限界法

#include 
#include 
using namespace std;

#define inf 1000000
#define NUM 100
int n;
int a[NUM][NUM];
int NoEdge = inf;
int cc;
int bestc;

struct node
{
	friend bool operator < (const node& a,const node& b)
	{
		if(a.lcost > b.lcost)  return true;
		else return false;
	}
	int lcost;
	int rcost;
	int cc;
	int s;
	int x[NUM];
};

int queueTSP()
{
	priority_queue <node> H;
	int v[NUM];
	int minOut[NUM];
	int minSum = 0;
	int i, j;
	for(i=1; i<=n; i++)
	{
		int Min = NoEdge;
		for(j=1; j<=n; j++)
			if(a[i][j]!=NoEdge && (a[i][j]<Min || Min==NoEdge))
				Min = a[i][j];
		if (Min==NoEdge)  return NoEdge;
		minOut[i] = Min;
		minSum += Min;
	}
	node E;
	for(i=1; i<=n; i++)
		E.x[i] = i;
	E.s = 1;
	E.cc = 0;
	E.rcost = minSum;
	int bestc = NoEdge;
	while (E.s<n)
	{
		if (E.s==n-1)
		{
			if (a[E.x[n-1]][E.x[n]]!=NoEdge && a[E.x[n]][1]!=NoEdge 
				&& (E.cc+a[E.x[n-1]][E.x[n]]+a[E.x[n]][1]<bestc 
				|| bestc==NoEdge))
			{
				bestc = E.cc+a[E.x[n-1]][E.x[n]]+a[E.x[n]][1];
				E.cc = bestc;
				E.lcost = bestc;
				E.s++;
				H.push(E);
			}
			else delete[] E.x;
		}
		else
		{
			for (i=E.s+1; i<=n; i++)
				if (a[E.x[E.s]][E.x[i]]!=NoEdge)
				{
					int cc = E.cc+a[E.x[E.s]][E.x[i]];
					int rcost = E.rcost-minOut[E.x[E.s]];
					int B = cc+rcost;
					if(B<bestc || bestc==NoEdge)
					{
						node N;
						for(j=1; j<=n; j++)
							N.x[j] = E.x[j];
						N.x[E.s+1] = E.x[i];
						N.x[i] = E.x[E.s+1];
						N.cc = cc;
						N.s = E.s+1;
						N.lcost = B;
						N.rcost = rcost;
						H.push(N);
					}
				}
				delete [] E.x;
		}
		if(H.empty()) break;
		else
		{
			E=H.top();
			H.pop();
		}
	}
	if (bestc==NoEdge) return NoEdge;
	for(i=1; i<=n; i++)
		printf("%d ",  E.x[i]);
	printf("\n");
	while (!H.empty()) H.pop();
	return bestc;
}

int main()
{
	int m;
	while(scanf("%d%d", &n, &m) !=EOF)
	{
		int i, j;
		for(i=0; i<=n; i++)
			for(j=0; j<=n; j++)
				a[i][j] = inf;
		int from, to, length;
		for(i=0; i<m; i++)
		{
			scanf("%d%d%d", &from, &to, &length);
			a[from][to] = length;
			a[to][from] = length;
		}
		cc = 0;
		bestc = 0;
		printf("%d\n", queueTSP());
	}
}