Added Bellmen_Ford Algorithm

Updated the file

Author: Abhishek-kumar82078

Graph_Algorithms/src/Bellmen_Ford_Algorithm/Bellmen_Ford.cpp

@@ -0,0 +1,65 @@
+//Bellmen Ford algorithm to detect negative weight cycle
+//Time Complexity is O(V*E)
+//Space Complexity is O(V)
+
+#include<bits/stdc++.h>
+using namespace std;
+#define inf INT_MAX
+
+int main()
+{
+  int v,e;      //V=total vertices  e=total edges
+  cin>>v>>e;
+  vector<vector<int>>edges;
+  for(int i=0;i<e;i++)
+  {
+    int x,y,w;
+    cin>>x>>y>>w;
+    edges.push_back({x,y,w});
+  }
+
+  //dis will store the minimum weight of that vertex
+  int dis[v]={inf};
+  dis[0]=0;
+
+  for(int i=1;i<v;i++)
+  {
+   for(int j=0;j<e;j++)
+   {
+   int x=edges[j][0];
+   int y=edges[j][1];
+   int wt=edges[j][2];
+     if(dis[y] > dis[x]+wt)
+       dis[y]=dis[x]+wt;
+   }
+  }
+
+
+  int flag=0;
+  for(int j=0;j<e;j++)
+   {
+   int x=edges[j][0];
+   int y=edges[j][1];
+   int wt=edges[j][2];
+     if(dis[y] > dis[x]+wt)
+     {
+       dis[y]=dis[x]+wt;
+       flag=1;
+     }
+   }
+
+   // If flag becomes 1 it means weight of vertex is still decreasing Hence is negative weight cycle
+  if(flag)
+   cout<<"Yes, this graph has negative weight cycle.";
+  else
+   cout<<"No, this graph doesn't have negative weight cycle.";
+
+ return 0;
+
+}
+
+
+/*Description
+If we iterate through all edges v-1 times then it guarantees the shortest distance of vettices.
+If we again iterate through all edges one more time and get a shorter path for any vertex,
+then there is a negative weight cycle.  */