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《数据结构与算法分析——C语言描述》  第九章

O（V^2)

void unweighed(Vertex srcVex,Graph g) {
int currDist;
Vertex v, w;

int *known = (int *)malloc(sizeof(int)*vexNum);
if (known == NULL)
Error("OUT OF MEMORY");
for (int i = 0; i < vexNum; i++)
known[i] = 0;

int *dv = (int *)malloc(sizeof(int)*vexNum);
if (dv == NULL)
Error("OUT OF MEMORY");
for (int i = 0; i < vexNum; i++)
dv[i] = INT_MAX;
dv[srcVex] = 0;

int *pv = (int *)malloc(sizeof(int)*vexNum);
if (pv == NULL)
Error("OUT OF MEMORY");
for (int i = 0; i < vexNum; i++)
pv[i] = srcVex;

for (currDist = 0; currDist < vexNum; currDist++) {
for (v = 0; v < vexNum; v++) {
if (!known[v] && dv[v] == currDist) {
known[v] = 1;
EdgeNodePtr p = getEdgeNodePtr(v, g);
while (p) {
w = getVex(p);
if (dv[w] == INT_MAX) {
dv[w] = currDist + 1;
pv[w] = v;
}
p = advance(p);
}
}

}
}
for (int i = 0; i < vexNum; i++) {

int j = i;
if (known[j] == 1) {
std::stack<int> s;
if (j != srcVex)
s.push(j);
while (pv[j] != srcVex) {
s.push(pv[j]);
j = pv[j];
}
s.push(pv[j]);
while (!s.empty()) {
printf("%d ", s.top());
s.pop();
}
printf("\n");
}
else {
printf("cannot reach\n");
}
}
}

O(E+V),书上的代码有点小错，从队列里弹出一个点没有判断这个点是否访问过。应该加上判断，已经访问过就不用再处理这个点。例如多个点同时邻接到一个点的时候，这个点就会多次加入到一个队列中。所以从队列里弹出来的点有可能是访问过的。

void unweighed(Vertex srcVex, Graph g) {
Vertex v, w;

int *known = (int *)malloc(sizeof(int)*vexNum);
if (known == NULL)
Error("OUT OF MEMORY");
for (int i = 0; i < vexNum; i++)
known[i] = 0;

int *dv = (int *)malloc(sizeof(int)*vexNum);
if (dv == NULL)
Error("OUT OF MEMORY");
for (int i = 0; i < vexNum; i++)
dv[i] = INT_MAX;
dv[srcVex] = 0;

int *pv = (int *)malloc(sizeof(int)*vexNum);
if (pv == NULL)
Error("OUT OF MEMORY");
for (int i = 0; i < vexNum; i++)
pv[i] = srcVex;

std::queue<int> q;
q.push(srcVex);
while (!q.empty()) {
v = q.front();
q.pop();

if (known[v] == 0) {
known[v] = 1;

EdgeNodePtr p = getEdgeNodePtr(v, g);
while (p) {
w = getVex(p);
dv[w] = dv[v] + 1;
pv[w] = v;
q.push(w);
p = advance(p);
}
}

}

for (int i = 0; i < vexNum; i++) {

int j = i;
if (known[j] == 1) {
std::stack<int> s;
if (j != srcVex)
s.push(j);
while (pv[j] != srcVex) {
s.push(pv[j]);
j = pv[j];
}
s.push(pv[j]);
while (!s.empty()) {
printf("%s ", nameRecord[s.top()]);
s.pop();
}
printf("\n");
}
else {
printf("cannot reach\n");
}
}
}