Merge pull request #45 from iamnidheesh/patch-1

Create Dijkstra.cpp

Graph/Dijkstra.cpp

@@ -0,0 +1,49 @@
+#include <queue>
+#include <vector>
+#include <cstdio>
+#include <iostream>
+using namespace std;
+#define INF 10000010
+vector < pair <int,int> > graph[5*100001];
+int dis[5*100001];
+int dij(vector <pair<int,int> > * v,int s,int * dis) {
+    priority_queue < pair <int,int> , vector < pair <int,int> >,greater < pair <int,int> > > pq;
+    // source distance to zero.
+    pq.push(make_pair(0,s));
+    dis[s] = 0;
+    int u;
+    while(!pq.empty()) {
+        u = (pq.top()).second;
+        pq.pop();
+        for( vector <pair <int,int> > :: iterator it = v[u].begin(); it != v[u].end();it++) {
+            if(dis[u] + it->first < dis[it->second]) {
+                dis[it->second] = dis[u] + it->first;
+                pq.push(make_pair(dis[it->second],it->second));
+            }
+        }
+    }
+}
+int main() {
+    int m,n,l,x,y,s;
+    // n--> number of nodes , m --> number of edges
+    cin>>n>>m;
+    for(int i = 0;i < m;i++) {
+        // input edges.
+        scanf("%d%d%d",&x,&y,&l);
+        graph[x].push_back(make_pair(l,y));
+        graph[y].push_back(make_pair(l,x)); // comment this line for directed graph
+    }
+    // start node.
+    scanf("%d",&s);
+    // intialise all distances to infinity.
+    for(int i = 1;i <= n;i++)
+        dis[i] = INF;
+    dij(graph,s,dis);
+    
+    for(int i = 1;i <= n;i++)
+        if(dis[i] == INF)
+            cout<<"-1 ";
+        else
+            cout<<dis[i]<<" ";
+    return 0;
+}