HDU-2647 Reward 拓扑排序

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

typedef struct a
{
int sign;
struct a *next;
} E;

struct b
{
int cnt;
struct a *next;
} V[10005];

int queue[10005], front, rear, M, N, hash[10005];

void insert( int x, int y ) // 要求边为从y指向x;
{
E *e= ( E * )malloc( sizeof( E ) );
e-> sign= x;
e-> next= V[y]. next;
V[y]. next= e;
V[x]. cnt++;
}

void _free( int v )
{
if( V[v]. next== NULL )
{
return;
}
E *p= V[v]. next;
while( p )
{
V[p-> sign]. cnt--;
E *q= p;
p= p-> next;
free( q );
}
V[v]. next= NULL;
}

int main(  )
{
while( scanf( "%d %d", &N, &M )!= EOF )
{
front= rear= 0;
int cnt= 0;
memset( hash, 0, sizeof( hash ) );
memset( V, 0, sizeof( V ) );
for( int i= 1; i<= M; ++i ) // 有M组关系
{
int x, y;
scanf( "%d %d", &x, &y );
insert( x, y );
}
int sum= 0, base= 888, flag= 0;
while( cnt< N )
{
int sign= 0;
for( int i= 1; i<= N; ++i )
{
if( V[i]. cnt== 0&& !hash[i] )
{
hash[i]= 1;
sign= 1;
queue[rear++]= i;
}
}
if( !sign )
{
flag= 1;
break;
}
while( front!= rear )
{
_free( queue[front++] );
cnt++;
sum+= base;
}
base++;
}
printf( flag? "-1\n": "%d\n", sum );
}
}
/*
2 1
1 2
2 2
1 2
2 1

5 4
1 2
2 3
2 4
1 5
*/