Following is the code I have written.
#include <iostream>
#include <vector>
#include <list>
#include <queue>
using namespace std;
const int V=5;
vector<list<int> > a(V);
int BFS(int s)
{
int visited[V]={0};
queue<int> Q;
visited[s]=1;
Q.push(s);
while(!Q.empty())
{
int x=Q.front();
vector<list<int> >::iterator it1=a.begin()+x;
list<int> it2=*it1;
list<int>::iterator iter=it2.begin();
while(iter!=it2.end())
{
if(visited[*iter]==0)
{
visited[*iter]=1;
Q.push(*iter);
}
visited[x]=2;
Q.pop();
iter++;
}
}
return 0;
}
void addEdge(int i, int j)
{
a[i].push_back(j);
a[j].push_back(i);
}
int main() {
vector<list<int> >::iterator it1=a.begin();
addEdge(0,1);
addEdge(0,2);
addEdge(2,1);
while(it1!=a.end())
{
list<int> it2=*it1;
list<int>::iterator iter=it2.begin();
while(iter!=it2.end())
{
cout<<*iter<<" ";
iter++;
}
cout<<endl;
it1++;
}
cout<<BFS(0);
return 0;
}
The compiler gives me a runtime error when BFS(0) is executed. Since I do not have much experience with iterators, I think the error comes from the iterator statements in the BFS function. Please help me resolve the issues in my code.
Thank you!
Your pop-logic is wrong. It should look like this:
int BFS(int s)
{
int visited[V]={0};
queue<int> Q;
visited[s]=1;
Q.push(s);
while(!Q.empty())
{
int x=Q.front();
Q.pop(); // pop here. we have x now
vector<list<int> >::iterator it1=a.begin()+x;
list<int> it2=*it1;
list<int>::iterator iter=it2.begin();
while(iter!=it2.end())
{
if(visited[*iter]==0)
{
visited[*iter]=1;
Q.push(*iter);
}
++iter;
}
visited[x]=2; // set visited here.
}
return 0;
}
Calculation of the final value I leave to you, as I imagine you want something besides zero always being returned. However, that was the crux of your problem.
Best of luck.
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