題目：改造拓?fù)渑判蛩惴ǎ靡耘袛嘤邢驁D是否有環(huán)路存在。

bool ExitCircle(ALGraph G)

{

?????? int* degree = (int*)malloc(G.vexnum * sizeof(int));

?????? NodeDegree(G, degree);

?????? Sqstack S;//零入度的頂點棧

?????? InitStack(S);

?????? int v;

?????? for (v = 0; v < G.vexnum; v++)

?????? {

????????????? if (!degree[v])//入度為0則進棧

???????????????????? Push(S, v);

?????? }

?????? int count = 0;

?????? AcrNode* p;

?????? while (!StackEmpty(S))

?????? {

????????????? int i = Pop(S);

????????????? count++;

????????????? for (p = G.vertices[i].firstarc; p != NULL; p = p->nextarc)

????????????? {

???????????????????? int k = p->adjvex;

???????????????????? if (--degree[k] == 0)//如果入度減為0則入棧

??????????????????????????? Push(S, k);

????????????? }

?????? }

?????? if (count < G.vexnum)

????????????? return true;

?????? return false;

}