【HDOJ】4109 Instrction Arrangement
差分约束。
1 /* 4109 */ 2 #include <iostream> 3 #include <queue> 4 #include <vector> 5 #include <algorithm> 6 #include <cstdio> 7 #include <cstring> 8 #include <cstdlib> 9 #include <climits> 10 using namespace std; 11 12 #define MAXV 1005 13 #define MAXE 41005 14 #define INF 0x3f 15 16 typedef struct { 17 int v, w, next; 18 } Edge_t; 19 20 Edge_t E[MAXE]; 21 int head[MAXV], L; 22 int dis[MAXV]; 23 bool visit[MAXV]; 24 int n, m; 25 26 void init() { 27 for (int i=0; i<=n; ++i) 28 dis[i] = INT_MIN; 29 memset(head, -1, sizeof(int)*(n+1)); 30 memset(visit, false, sizeof(bool)*(n+1)); 31 L = 0; 32 } 33 34 void addEdge(int u, int v, int w) { 35 E[L].v = v; 36 E[L].w = w; 37 E[L].next = head[u]; 38 head[u] = L++; 39 } 40 41 void spfa() { 42 int i, j, k; 43 int u, v, w; 44 queue<int> Q; 45 46 visit[n] = true; 47 dis[n] = 0; 48 Q.push(n); 49 50 while (!Q.empty()) { 51 u = Q.front(); 52 Q.pop(); 53 visit[u] = false; 54 for (i=head[u]; i!=-1; i=E[i].next) { 55 v = E[i].v; 56 w = E[i].w; 57 if (dis[v] < dis[u]+w) { 58 dis[v] = dis[u] + w; 59 if (!visit[v]) { 60 visit[v] = true; 61 Q.push(v); 62 } 63 } 64 } 65 } 66 } 67 68 int main() { 69 int i, j, k; 70 71 #ifndef ONLINE_JUDGE 72 freopen("data.in", "r", stdin); 73 freopen("data.out", "w", stdout); 74 #endif 75 76 while (scanf("%d %d",&n,&m) != EOF) { 77 init(); 78 while (m--) { 79 scanf("%d%d%d", &i, &j, &k); 80 addEdge(j, i, k); 81 } 82 for (i=0; i<n; ++i) 83 addEdge(n, i, 0); 84 spfa(); 85 k = INT_MIN; 86 for (i=0; i<=n; ++i) 87 k = max(k, dis[i]); 88 printf("%d\n", k+1); 89 } 90 91 return 0; 92 }
