数据结构1 - 08-图8 How Long Does It Take

 

 

#include<stdio.h>
#include<string.h>
#define MAXN 100
#define INF 0x3fffffff
int n,m,g[MAXN][MAXN],indegree[MAXN],ve[MAXN];
void read();
int topsort(); 
int main(){
    int cost;
    read();
    cost = topsort();
    if(cost==-1) printf("Impossible\n");
    else printf("%d",cost);
    return 0;
}
void read(){
    scanf("%d %d",&n,&m);
    int i,j,v1,v2,lastime;
    for(i=0;i<n;i++)
        for(j=0;j<n;j++)
            g[i][j] = INF;
    for(i=0;i<n;i++) indegree[i]=0;
    for(i=0;i<m;i++){
        scanf("%d %d %d",&v1,&v2,&lastime);
        g[v1][v2] = lastime;
        indegree[v2]++;
    }
}
int topsort(){
    int i,j,count=0,seq[MAXN];
    int cost,time,point;
    for(i=0;i<n;i++) ve[i] = 0;
    j=0;
    for(i=0;i<n;i++){
        if(indegree[i]==0)seq[j++] = i;
    }
    count = j;
    j=0;
    while(count>j){
        point = seq[j];
        j++;
        for(i=0;i<n;i++){
            if(g[point][i]!=INF&&i!=point){
                indegree[i]--;
                if(ve[i]<ve[point]+g[point][i])
                    ve[i] = ve[point]+g[point][i];
                if(indegree[i]==0){
                    seq[count++] = i;
                }
            }
        }
        
    }
    if(count==n){
        cost = 0;
        for(i=0;i<n;i++){
            if(cost<ve[i]) cost = ve[i];
        }
        return cost;
    }
    else return -1;
        
}