Ladder match practice --7-15 How Long Does It Take (25 points) (Critical Path + topological sorting)

topic:

analysis:

Determining whether the topological sort to complete the project (i.e., determines whether there is a loop), if it can complete the project, the required maximum time needed to complete the project, it is worth noting that the maximum time n-1 is not necessarily at this point, could 0 to any point in the n-1, the last cycle time required to find the longest time.

Code:

#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
#include <vector>
#define INF 0x3f3f3f3f
using namespace std;

const int MAXN = 105;
int n,m;
int ve[MAXN],inDegree[MAXN];
int mat[MAXN][MAXN];
queue<int> q;

bool Topological()
{
    int cnt = 0;
    for(int i=0;i<n;++i)
        if(inDegree[i]==0)
            q.push(i);
    while(!q.empty())
    {
        int now = q.front();
        cnt++;
        q.pop();
        for(int i=0;i<n;++i)
        {
            if(mat[now][i]!=INF)
            {
                inDegree[i]--;
                if(inDegree[i] == 0)
                    q.push(i);
                if(ve[now]+mat[now][i] > ve[i])
                    ve[i] = ve[now] + mat[now][i];
            }
        }
    }
    if(cnt == n) return true;
    else return false;
}

int main()
{
    scanf("%d%d",&n,&m);
    int st,ed,ti;
    memset(mat,INF,sizeof(mat));
    for(int i=1;i<=m;++i)
    {
        scanf("%d%d%d",&st,&ed,&ti);
        mat[st][ed] = ti;
        inDegree[ed]++;
    }
    bool flag = Topological();
    int ans = 0;
    if(!flag)
        printf("Impossible\n");
    else
    {
        for(int i=0;i<n;++i)
            ans = max(ans,ve[i]);
        printf("%d\n",ans);
    }
    return 0;
}