HDU 2647 Reward (topological sort)

1. Reverse mapping is useful for calculating

2. Code:

#include <cstdio> #include <cstring> #include <stdlib.h> #define MAX (b) ((a) > (c)? (    A):(B)) using namespace std;typedef struct arcnode{int adjvex; struct Arcnode * NEXTARC;}    arcnode;typedef struct vnode{int vertex; Arcnode * FIRSTARC;} Vnode;int N,m;int stack[10005];    Vnode v[10005];int top;int in[10005];int level[10005];void free () {Arcnode * p;    Arcnode * q;        for (int i=1;i<=n;i++) {P=v[i].firstarc;            while (p!=null) {q=p->nextarc;            Free (p);        p=q;    }}}int Main () {int a A, B;    Arcnode * p;        while (scanf ("%d%d", &n,&m) ==2) {top=0;        memset (stack,0,sizeof (Stack));            for (int i=1; i<=n; i++) {v[i].vertex=i;            V[i].firstarc=null;            level[i]=888;        in[i]=0;            } for (int i=1; i<=m; i++) {scanf ("%d%d", &a,&b);            in[a]++; p= (Arcnode *) malloc (sizeof (Arcnode));            p->adjvex=a;            p->nextarc=v[b].firstarc;        V[b].firstarc=p;        } memset (Level) (level,0,sizeof);                for (int i=1; i<=n; i++) {if (in[i]==0) {Stack[++top]=v[i].vertex;            level[i]=888;        }} int cnt=0;            while (top!=0) {int j=stack[top--];            cnt++;                for (P=V[J].FIRSTARC; p; p=p->nextarc) {int k=p->adjvex;                in[k]--;                Level[k]=max (Level[j]+1,level[k]);                    if (in[k]==0) {stack[++top]=k;                Level[k]=max (Level[j]+1,level[k]);            }}} if (cnt==n) {int ans=0;            for (int i=1;i<=n;i++) {ans+= (level[i]);        } printf ("%d\n", ans);        } else printf (" -1\n");  Free ();  } return 0;} 

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HDU 2647 Reward (topological sort)