backup/C-Plus-Plus
1
0
Fork 0
mirror of https://github.com/TheAlgorithms/C-Plus-Plus.git synced 2026-04-09 05:29:13 +08:00
Code Issues Projects Releases Wiki Activity

Updated function definitions with comments

Browse Source 
function definitions - what it does with its type (iterative/recursive) 
common terms/annotations
2 statements marked as debug, removed other comments (as I kept them while coding)
added comments to main function
This commit is contained in:
Anirban Chetia
2019-11-21 22:11:24 +05:30
committed by GitHub
parent 5da2760d3f
commit 0ef5cbec29
1 changed files with 33 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

54
Graph/Kosaraju.cpp
View File

@@ -1,12 +1,20 @@
/* Implementation of Kosaraju's Algorithm to find out the strongly connected components (SCCs) in a graph.
Author:Anirban166
*/
*/
#include<iostream>
#include<vector>
using namespace std;
/*Common terms/anotations used as parameters in functions below:
V: number of vertices,
adj[]: array of vectors to represent graph,
vis[]: array to keep track of visited nodes, (boolean type)
grev[]: graph with reverse edges.
*/
//iterative function/method to print graph:
void print(vector<int> a[],int V)
{
for(int i=0;i<V;i++)
@@ -19,16 +27,20 @@ void print(vector<int> a[],int V)
cout<<endl;
}
}
void calculate_time(int v,stack<int> &st,bool vis[],vector<int> adj[])
//recursive function/method to push vertices into stack passed as parameter: (referenced)
void push_vertex(int v,stack<int> &st,bool vis[],vector<int> adj[])
{
vis[v]=true;
for(auto i=adj[v].begin();i!=adj[v].end();i++)
{
if(vis[*i]==false)
calculate_time(*i,st,vis,adj);
push_vertex(*i,st,vis,adj);
}
st.push(v);
}
//recursive function/method to implement depth first traversal(dfs):
void dfs(int v,bool vis[],vector<int> grev[])
{
vis[v]=true;
@@ -39,18 +51,18 @@ void dfs(int v,bool vis[],vector<int> grev[])
dfs(*i,vis,grev);
}
}
//function/method to implement Kosaraju's Algorithm:
int kosaraju(int V, vector<int> adj[])
{
// print(adj,V);
bool vis[V]={};
stack<int> st;
for(int v=0;v<V;v++)
{
if(vis[v]==false)
calculate_time(v,st,vis,adj);
push_vertex(v,st,vis,adj);
}
// cout<<"stack_size="<<st.size()<<endl;
//making new graph (grev) with reverse edges as in adj[]
//making new graph (grev) with reverse edges as in adj[]:
vector<int> grev[V];
for(int i=0;i<V+1;i++)
{
@@ -59,12 +71,12 @@ int kosaraju(int V, vector<int> adj[])
grev[*j].push_back(i);
}
}
// cout<<"grev="<<endl;
// print(grev,V);
// cout<<"grev="<<endl; ->debug statement
// print(grev,V); ->debug statement
//reinitialise visited to 0
for(int i=0;i<V;i++)
vis[i]=false;
int cnt_scc=0;
int count_scc=0;
while(!st.empty())
{
int t=st.top();
@@ -72,13 +84,13 @@ int kosaraju(int V, vector<int> adj[])
if(vis[t]==false)
{
dfs(t,vis,grev);
cnt_scc++;
count_scc++;
}
}
// cout<<"cnt_scc="<<cnt_scc<<endl;
return cnt_scc;
// cout<<"count_scc="<<count_scc<<endl; //in case you want to print here itself, uncomment & change return type of function to void.
return count_scc;
}
//All critical/corner cases have been taken care of.
//Input your required values: (not hardcoded)
int main()
@@ -87,16 +99,16 @@ int main()
cin>>t;
while(t--)
{
int a,b ;
cin>>a>>b;
int m,n;
vector<int> adj[a+1];
for(int i=0;i<b;i++)
int a,b ; //a->number of nodes, b->directed edges.
cin>>a>>b;
int m,n;
vector<int> adj[a+1];
for(int i=0;i<b;i++) //take total b inputs of 2 vertices each required to form an edge.
{
cin>>m>>n;
cin>>m>>n; //take input m,n denoting edge from m->n.
adj[m].push_back(n);
}
// exit(0);
//pass number of nodes and adjacency array as parameters to function:
cout<<kosaraju(a, adj)<<endl;
}
return 0;