3 graph algos

Author: dobhsh

graph/c++/bellman.cpp

@@ -0,0 +1,69 @@
+#include<iostream>
+#include<bits/stdc++.h>
+using namespace std;
+int e,v;
+struct edge
+{
+char v1,v2;
+int w;
+}*E;
+struct vertex
+{
+char v,P;
+int d;
+}*V;
+bool BellmanFord(char s)
+{
+V[s-97].d=0;
+for(int j=1;j<v;j++)
+{
+for(int i=0;i<e;i++)
+{
+if(E[i].w+V[(E[i].v1)-97].d<V[(E[i].v2)-97].d)
+{
+V[(E[i].v2)-97].P=E[i].v1;
+V[(E[i].v2)-97].d=E[i].w+V[(E[i].v1)-97].d;
+}
+}
+}
+for(int i=0;i<e;i++)
+{
+if(E[i].w+V[(E[i].v1)-97].d<V[(E[i].v2)-97].d)
+return false;
+}
+return true;
+}
+int main()
+{
+char s;
+cout<<"Enter no. of vertices: ";
+cin>>v;
+V=new vertex[v];
+cout<<"Enter no. of edges: ";
+cin>>e;
+E=new edge[e];
+cout<<"Enter edges and their weights: \n";
+for(int i=0;i<e;i++)
+cin>>E[i].v1>>E[i].v2>>E[i].w;
+for(int i=0;i<v;i++)
+{
+V[i].v=i+97;
+V[i].d=INT_MAX;
+V[i].P=' ';
+}
+cout<<"Enter the souce vertex: ";
+cin>>s;
+bool res=BellmanFord(s);
+if(res==false)
+{
+cout<<"Negative weight cycle exists in graph!!!\n";
+cout<<"Bellman Ford Algorithm Fails!!!";
+}
+else
+{
+cout<<"Shortest Distance from "<<s<<":\n";
+for(int i=0;i<v;i++)
+cout<<V[i].v<<" = "<<" \t "<<V[i].d<<endl;
+}
+return 0;
+}

graph/c++/dijikstra.cpp

@@ -0,0 +1,89 @@
+#include<iostream>
+using namespace std;
+int e,v;
+char *Q;
+struct edge
+{
+char v1,v2;
+int w;
+}*E;
+struct vertex
+{
+char v,P;
+int d;
+}*V;
+char Extract_Min()
+{
+char min;
+int k=INT_MAX;
+int pos;
+for(int i=0;i<v;i++)
+{
+if(k>V[i].d&&Q[i]!=' ')
+{
+min=Q[i];
+pos=i;
+k=V[i].d;
+}
+}
+Q[pos]=' ';
+return min;
+}
+void dijkstra(char s)
+{
+int qs=v;
+char u,r=Q[s-97];
+V[s-97].d=0;
+while(qs--)
+{
+u=Extract_Min();
+//cout<<u<<" ";
+for(int i=0;i<e;i++)
+{
+if(E[i].v1==u)
+{
+if((Q[(E[i].v2)-97]!=' ')&&((E[i].w+V[u-97].d)<V[(E[i].v2)-97].d))
+{
+V[(E[i].v2)-97].P=E[i].v1;
+V[(E[i].v2)-97].d=E[i].w+V[u-97].d;
+}
+}
+else if(E[i].v2==u)
+{
+if((Q[(E[i].v1)-97]!=' ')&&((E[i].w+V[u-97].d)<V[(E[i].v1)-97].d))
+{
+V[(E[i].v1)-97].P=E[i].v2;
+V[(E[i].v1)-97].d=E[i].w+V[u-97].d;
+}
+}
+}
+}
+}
+int main()
+{
+char s;
+cout<<"Enter no. of vertices: ";
+cin>>v;
+V=new vertex[v];
+Q=new char[v];
+cout<<"Enter no. of edges: ";
+cin>>e;
+E=new edge[e];
+cout<<"Enter edges and their weights: \n";
+for(int i=0;i<e;i++)
+cin>>E[i].v1>>E[i].v2>>E[i].w;
+for(int i=0;i<v;i++)
+{
+V[i].v=i+97;
+V[i].d=INT_MAX;
+V[i].P=' ';
+Q[i]=i+97;
+}
+cout<<"Enter the souce vertex: ";
+cin>>s;
+dijkstra(s);
+cout<<"Shortest Distance from "<<s<<":\n";
+for(int i=0;i<v;i++)
+cout<<V[i].v<<" = "<<" \t "<<V[i].d<<endl;
+return 0;
+}

graph/c++/floyd_warshall.cpp

@@ -0,0 +1,99 @@
+#include<iostream>
+#include<climits>
+#include<bits/stdc++.h>
+using namespace std;
+int v,e;
+int **W;
+struct matrix
+{
+int **D;
+char **P;
+}*R;
+void Floyd_Warshall(int **W,int n)
+{
+R=new matrix[n+1];
+for(int i=0;i<=n;i++)
+{
+R[i].D=new int*[n];
+R[i].P=new char*[n];
+for(int k=0;k<n;k++)
+{
+R[i].D[k]=new int[n];
+R[i].P[k]=new char[n];
+}
+}
+for(int i=0;i<n;i++)
+{
+for(int j=0;j<n;j++)
+{
+R[0].D[i][j]=W[i][j];
+if(W[i][j]==INT_MAX||W[i][j]==0)
+R[0].P[i][j]='N';
+else
+R[0].P[i][j]=i+97;
+}
+}
+for(int k=1;k<=n;k++)
+{
+for(int i=0;i<n;i++)
+{
+for(int j=0;j<n;j++)
+{
+if(R[k-1].D[i][j]>(R[k-1].D[i][k-1]+R[k-1].D[k-1][j])&&
+ R[k-1].D[i][k-1]!=INT_MAX&&R[k-1].D[k-1][j]!=INT_MAX)
+{
+R[k].D[i][j]=R[k-1].D[i][k-1]+R[k-1].D[k-1][j];
+R[k].P[i][j]=R[k-1].P[k-1][j];
+}
+else
+{
+R[k].D[i][j]=R[k-1].D[i][j];
+R[k].P[i][j]=R[k-1].P[i][j];
+}
+}
+}
+}
+}
+int main()
+{
+char a,b;
+int w;
+cout<<"Enter the no. of vertices: ";
+cin>>v;
+W=new int*[v];
+cout<<"Enter the no. of edges: ";
+cin>>e;
+for(int i=0;i<v;i++)
+{
+W[i]=new int[v];
+for(int j=0;j<v;j++)
+{
+if(i==j)
+W[i][j]=0;
+else
+W[i][j]=INT_MAX;
+}
+}
+cout<<"Enter edges and their corresponding weights: \n";
+for(int i=0;i<e;i++)
+{
+cin>>a>>b>>w;
+W[a-97][b-97]=w;
+}
+Floyd_Warshall(W,v);
+cout<<"Distance Matrix: \n";
+for(int i=0;i<v;i++)
+{
+for(int j=0;j<v;j++)
+cout<<R[v].D[i][j]<<"\t";
+cout<<endl;
+}
+cout<<"Parent Matrix: \n";
+for(int i=0;i<v;i++)
+{
+for(int j=0;j<v;j++)
+cout<<R[v].P[i][j]<<"\t";
+cout<<endl;
+}
+return 0;
+}