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January 26, 2016 10:05
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Breadth First Search Algorithm; C++ Implementation
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#include <iostream> | |
#include <vector> | |
#include <list> | |
#include <algorithm> | |
#include<stdlib.h> | |
using namespace std; | |
class Graph | |
{ | |
int V; | |
vector<int> *adj; | |
vector<int> *wgt; | |
int *prev; | |
public: | |
Graph(int V); | |
void addEdge(int v, int w, int wgt); | |
void BFS(int s, int t); | |
void displayPath(int f); | |
}; | |
Graph::Graph(int V) | |
{ | |
this->V = V; | |
adj = new vector<int>[V]; | |
wgt = new vector<int>[V]; | |
prev = new int[V]; | |
} | |
void Graph::addEdge(int v, int w, int wt) { | |
adj[v].push_back(w); | |
wgt[v].push_back(wt); | |
adj[w].push_back(v); | |
wgt[w].push_back(wt); | |
} | |
void Graph::BFS(int s, int t) { | |
bool *visited = new bool[V]; | |
for (int i = 0; i < V; ++i) { | |
visited[i] = false; | |
} | |
list<int> queue; | |
int current; | |
visited[s] = true; | |
prev[s] = -1; | |
queue.push_back(s); | |
vector<int>::iterator i; | |
while(!queue.empty()) | |
{ | |
current = queue.front(); | |
queue.pop_front(); | |
for (i = adj[current].begin(); i != adj[current].end(); ++i) | |
{ | |
if(!visited[*i]) | |
{ | |
prev[*i] = current; | |
visited[*i] = true; | |
if(*i == t) | |
{ | |
cout<<"found"<<endl; | |
displayPath(t); | |
exit(0); | |
} | |
queue.push_back(*i); | |
} | |
} | |
} | |
} | |
void Graph::displayPath(int f) | |
{ | |
int p = f; | |
int q; | |
int pos; | |
int pathlen = 0; | |
cout<<"Path is: "; | |
while(p!=-1) | |
{ | |
cout<<"->"<<p; | |
q = prev[p]; | |
if(q!=-1) | |
{ | |
pos = find(adj[p].begin(), adj[p].end(), q) - adj[p].begin(); | |
pathlen = pathlen + wgt[p].at(pos); | |
} | |
p = q; | |
} | |
cout<<endl; | |
cout<<"pathlength : "<<pathlen; | |
cout<<endl; | |
} | |
int main() | |
{ | |
int n,e, a, b, c; | |
int vstart, vend; | |
cout<<"No. of vertices:"; | |
cin>>n; | |
cout<<"No. of edges:"; | |
cin>>e; | |
Graph g(n); | |
cout<<"Enter the list of edges in the format : v1 v2 weight:"; | |
for(int i = 0; i<e; i++) | |
{ | |
cin>>a>>b>>c; | |
g.addEdge(a, b, c); | |
} | |
cout<<"Enter the start vertex:"; | |
cin>>vstart; | |
cout<<"Enter the end vertex:"; | |
cin>>vend; | |
g.BFS(vend, vstart); | |
return 0; | |
} | |
/* | |
g.addEdge(0, 1, 12); | |
g.addEdge(0, 2, 8); | |
g.addEdge(0, 3, 7); | |
g.addEdge(1, 4, 8); | |
g.addEdge(1, 5, 7); | |
g.addEdge(2, 6, 6); | |
g.addEdge(2, 7, 5); | |
g.addEdge(3, 8, 4); | |
g.addEdge(3, 9, 3); | |
*/ |
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