main()
{
PATH path;
NODE root = {
0, /* 花费下界 */
{{{I, 1, 2, 7, 5}, /* 花费矩阵 */
{1, I, 4, 4, 3},
{2, 4, I, 1, 2},
{7, 4, 1, I, 3},
{5, 3, 2, 3, I}}, 5}, /* 城市数目 */
{{0}, 0}, /* 经历过的路径 */
NULL, NULL /* 左枝与右枝 */
};
/* 归约，建立根结点 */
root.bound += Simplify(&root.matrix);
/* 进入搜索循环 */
path = BABA(root);
ShowPath(path, root.matrix);
}
/*
* 算法主搜索函数，Branch-And-Bound Algorithm Search
* root 是当前的根结点，已归约，数据完善
*/
PATH BABA(NODE root)
{
int i;
static int minDist = INFINITY;
static PATH minPath;
EDGE selectedEdge;
NODE *left, *right;
puts("Current Root:\n------------");
ShowMatrix(root.matrix);
printf("Root Bound:%d\n", root.bound);
/* 如果当前矩阵大小为2，说明还有两条边没有选，而这两条边必定只能有一种组合，
* 才能构成整体回路，所以事实上所有路线已经确定。
*/
if (MatrixSize(root.matrix, root.path) == 2) {
if (root.bound < minDist) {
minDist = root.bound;
minPath = MendPath(root.path, root.matrix);
getch();
return (minPath);
}
}
/* 根据左下界尽量大的原则选分枝边 */
selectedEdge = SelectBestEdge(root.matrix);
printf("Selected Edge:(%d, %d)\n", selectedEdge.head + 1, selectedEdge.tail + 1);
/* 建立左右分枝结点 */
left = (NODE *)malloc(sizeof(NODE));
right = (NODE *)malloc(sizeof(NODE));
if (left == NULL || right == NULL) {
fprintf(stderr,"Error malloc.\n");
exit(-1);
}
/* 初始化左右分枝结点 */
left->bound = root.bound; /* 继承父结点的下界 */
left->matrix = LeftNode(root.matrix, selectedEdge); /* 删掉分枝边 */
left->path = root.path; /* 继承父结点的路径，没有增加新边 */
left->left = NULL;
left->right = NULL;
right->bound = root.bound;
right->matrix = RightNode(root.matrix, selectedEdge, root.path);/* 删除行列和回路边 */
right->path = AddEdge(selectedEdge, root.path); /* 加入所选边 */
right->left = NULL;
right->right = NULL;
/* 归约左右分枝结点 */
left->bound += Simplify(&left->matrix);
right->bound += Simplify(&right->matrix);
/* 链接到根 */
root.left = left;
root.right = right;
/* 显示到监视器 */
puts("Right Branch:\n------------");
ShowMatrix(right->matrix);
puts("Left Branch:\n-----------");
ShowMatrix(left->matrix);
/* 如果右结点下界小于当前最佳答案，继续分枝搜索 */
if (right->bound < minDist) {
BABA(*right);
}
/* 否则不搜索，因为这条枝已经不可能产生更佳路线 */
else {
printf("Current minDist is %d, ", minDist);
printf("Right Branch's Bound(= %d).\n", right->bound);
printf("This branch is dead.\n");
}
/* 如果右结点下界小于当前最佳答案，继续分枝搜索 */
if (left->bound < minDist) {
BABA(*left);
}
/* 否则不搜索，因为这条枝已经不可能产生更佳路线 */
else {
printf("Current minDist is %d, ", minDist);
printf("Left Branch's Bound(= %d).\n", left->bound);
printf("This branch is dead.\n");
}
printf("The best answer now is %d\n", minDist);
return (minPath);
}
