hdu Instrction Arrangement（关键路径 + 拓扑排序）

#include <stdio.h>
#include <queue>
#include <math.h>
#include <string.h>
#include <algorithm>
using namespace std;

const int N = 1007;

typedef struct Edge
{
    int w;
    int to;
    int next;
}edge;
edge eg[N * 10];

int n, m, head[N], isVis[N], in[N], out[N], val[N];  //val记录每个状态的时间，记录到达当前状态最长的时间
queue <int> q;

int criticalPath()
{
    int max = -1;
    while (!q.empty())
        q.pop();
    memset(val, 0, sizeof(val));
    for (int i = 0; i < n; i++)
    {
        if (!in[i])
        {
            val[i] = 1;
            q.push(i);
            isVis[i] = 1;
        }
    }
    while (!q.empty())
    {
        int temp = q.front();
        q.pop();
        if (val[temp] > max)
            max = val[temp];
        int r = head[temp];
        while (r != -1)
        {
            in[eg[r].to]--;
            if (val[eg[r].to] < val[temp] + eg[r].w - 1)
                val[eg[r].to] = val[temp] + eg[r].w - 1;
            if (!in[eg[r].to] && !isVis[eg[r].to])
            {
                val[eg[r].to]++;
                isVis[eg[r].to] = 1;
                q.push(eg[r].to);
            }
            r = eg[r].next;
        }
    }
    return max;
}

int main()
{
    while (scanf("%d%d", &n, &m) != EOF)
    {
        memset(isVis, 0, sizeof(isVis));
        memset(head, -1, sizeof(head));
        for (int i = 1; i <= m; i++)
        {
            int u, v, w;
            scanf("%d%d%d", &v, &u, &w);
            eg[i].to = v;
            eg[i].w = w;
            in[v]++;
            out[u]++;
            eg[i].next = head[u];
            head[u] = i;
        }
        printf("%d\n", criticalPath());
    }
    return 0;
}