【HDOJ】4109 Instrction Arrangement

差分约束。

 /* 4109 */
 #include <iostream>
 #include <queue>
 #include <vector>
 #include <algorithm>
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>
 #include <climits>
 using namespace std;

 #define MAXV 1005
 #define MAXE 41005
 #define INF  0x3f

 typedef struct {
     int v, w, next;
 } Edge_t;

 Edge_t E[MAXE];
 int head[MAXV], L;
 int dis[MAXV];
 bool visit[MAXV];
 int n, m;

 void init() {
     for (int i=; i<=n; ++i)
         dis[i] = INT_MIN;
     memset(head, -, sizeof(int)*(n+));
     memset(visit, false, sizeof(bool)*(n+));
     L = ;
 }

 void addEdge(int u, int v, int w) {
     E[L].v = v;
     E[L].w = w;
     E[L].next = head[u];
     head[u] = L++;
 }

 void spfa() {
     int i, j, k;
     int u, v, w;
     queue<int> Q;

     visit[n] = true;
     dis[n] = ;
     Q.push(n);

     while (!Q.empty()) {
         u = Q.front();
         Q.pop();
         visit[u] = false;
         for (i=head[u]; i!=-; i=E[i].next) {
             v = E[i].v;
             w = E[i].w;
             if (dis[v] < dis[u]+w) {
                 dis[v] = dis[u] + w;
                 if (!visit[v]) {
                     visit[v] = true;
                     Q.push(v);
                 }
             }
         }
     }
 }

 int main() {
     int i, j, k;

     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
         freopen("data.out", "w", stdout);
     #endif

     while (scanf("%d %d",&n,&m) != EOF) {
         init();
         while (m--) {
             scanf("%d%d%d", &i, &j, &k);
             addEdge(j, i, k);
         }
         for (i=; i<n; ++i)
             addEdge(n, i, );
         spfa();
         k = INT_MIN;
         for (i=; i<=n; ++i)
             k = max(k, dis[i]);
         printf("%d\n", k+);
     }

     return ;
 }