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| 1 | +/* Amit Bansal - @amitbansal7 */ |
| 2 | +#include <iostream> |
| 3 | +#include <vector> |
| 4 | +#include <stack> |
| 5 | +#include <limits.h> |
| 6 | +#define NINF INT_MIN |
| 7 | +using namespace std; |
| 8 | +using namespace std; |
| 9 | + |
| 10 | +/* Longest simple path in directed acyclic graph in O(V+E) */ |
| 11 | + |
| 12 | +void TopologicalSort(vector <pair< int, int> >adj[], int s, bool visited[], stack < int> &S) |
| 13 | +{ |
| 14 | + visited[s] = true; |
| 15 | + |
| 16 | + vector<pair<int, int> >::iterator it; |
| 17 | + for (it = adj[s].begin(); it != adj[s].end(); it++) |
| 18 | + if (!visited[it->first]) |
| 19 | + TopologicalSort(adj, it->first, visited, S); |
| 20 | + |
| 21 | + |
| 22 | + S.push(s); |
| 23 | +} |
| 24 | + |
| 25 | +void LSPDAG(vector <pair< int, int> >adj[], int s, int v) |
| 26 | +{ |
| 27 | + stack <int> S; |
| 28 | + bool visited[v]; |
| 29 | + memset(visited, false, sizeof(visited)); |
| 30 | + |
| 31 | + for (int i = 0; i < v; i++) |
| 32 | + if (!visited[i]) |
| 33 | + TopologicalSort(adj, i, visited, S); |
| 34 | + |
| 35 | + int dist[v]; |
| 36 | + |
| 37 | + for(int i=0;i<v;i++) |
| 38 | + dist[i] = NINF; |
| 39 | + |
| 40 | + dist[s] = 0; |
| 41 | + |
| 42 | + while (!S.empty()) |
| 43 | + { |
| 44 | + int u = S.top(); |
| 45 | + S.pop(); |
| 46 | + |
| 47 | + if (dist[u] != NINF) |
| 48 | + { |
| 49 | + vector <pair<int, int> >::iterator it; |
| 50 | + for (it = adj[u].begin(); it != adj[u].end(); ++it) |
| 51 | + if (dist[it->first] < dist[u] + it->second) |
| 52 | + dist[it->first] = dist[u] + it->second; |
| 53 | + } |
| 54 | + |
| 55 | + } |
| 56 | + |
| 57 | + for (int i = 0; i < v; i++) |
| 58 | + (dist[i] == NINF) ? cout << "-INF " : cout << dist[i] << " "; |
| 59 | + |
| 60 | + printf("\n"); |
| 61 | +} |
| 62 | + |
| 63 | +int main() |
| 64 | +{ |
| 65 | + vector <pair<int, int> >adj[6]; |
| 66 | + |
| 67 | + adj[0].push_back(make_pair(1, 5)); |
| 68 | + adj[0].push_back(make_pair(2, 3)); |
| 69 | + adj[1].push_back(make_pair(3, 6)); |
| 70 | + adj[1].push_back(make_pair(2, 2)); |
| 71 | + adj[2].push_back(make_pair(4, 4)); |
| 72 | + adj[2].push_back(make_pair(5, 2)); |
| 73 | + adj[2].push_back(make_pair(3, 7)); |
| 74 | + adj[3].push_back(make_pair(5, 1)); |
| 75 | + adj[3].push_back(make_pair(4, -1)); |
| 76 | + adj[4].push_back(make_pair(5, -2)); |
| 77 | + |
| 78 | + LSPDAG(adj, 1, 6); |
| 79 | + |
| 80 | + return 0; |
| 81 | +} |
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