HDU 3342 Legal or not

Test instructions: To judge whether there is no loop;

Idea: topological sequencing;

Two types of notation:

struct + pointer:

#include <stdio.h> #include <string.h> #include <algorithm>using namespace Std;int n,m;struct node{    int du; Node *next;}    Q[50010];int topo () {node *p;    int *shu=new int[50010];    int i,j,k=0,num;        while (1) {num=0;        memset (Shu,0,sizeof (SHU));            for (i=0;i<n;i++) {if (q[i].du==-1) continue;                if (q[i].du==0) {shu[num++]=i;                Q[i].du=-1;            k++;        }} if (Num==0&&k<=n) return 0;        if (k==n) return 1;            for (i=0;i<num;i++) {p=q[shu[i]].next;                while (p) {q[p->du].du--;            p=p->next;    }}}}int Main () {int a,b,i,k,j;        while (scanf ("%d%d", &n,&m)!=eof) {if (n==0&&m==0) break;            for (i=0;i<n;i++) {q[i].du=0;        Q[i].next=null; } for (i=0;i<m;i++) {           scanf ("%d%d", &a,&b);            q[a].du++;            Node *t=new node;            t->du=a;            t->next=q[b].next;        q[b].next=t;        } if (topo ()) printf ("yes\n");    else printf ("no\n"); } return 0;}

STL, queue:

#include <stdio.h> #include <string.h> #include <queue> #include <algorithm>using namespace std ; int con[500010],n,m;vector<int> G[500010];int topo () {    int sum=n;    queue<int> Q;    int flag=0;    for (int i=0;i<n;i++)        if (con[i]==0) Q.push (i);    while (!q.empty ())    {        sum--;        int J=q.front ();        Q.pop ();        for (int k=0;k<g[j].size (); k++)        {            if (--con[g[j][k]]==0) Q.push (G[j][k]);        }    }    if (sum>0) return 0;    else return 1;} int main () {    int i,j,k,a,b;    while (scanf ("%d%d", &n,&m)!=eof)    {        if (n==0&&m==0) break;        for (i=0;i<=n;i++)        {            con[i]=0;            G[i].clear ();        }        for (i=0;i<m;i++)        {            scanf ("%d%d", &a,&b);            G[a].push_back (b);            con[b]++;        }        if (topo ()) printf ("yes\n");        else printf ("no\n");    }    return 0;}

HDU 3342 Legal or not