Merge pull request larissalages#129 from Rishu-Xingh007/master

detect_cycle_dfs.cpp

Author: larissalages

CodeChef_problems/Zombies_and_Magic.cpp

@@ -0,0 +1,50 @@
+#include<bits/stdc++.h>
+#define ll long long
+#define N 100000
+using namespace std;
+
+vector<ll>adj[N];
+vector<ll>vis(N);
+void dfs(ll curr)
+{
+    vis[curr]=1;
+    for(auto neb:adj[curr])
+    {
+        if(vis[neb]==0)
+        dfs(neb);
+    }
+}
+int main()
+{
+    ll n,m;
+    cin>>n>>m;
+    ll z;
+    cin>>z;
+    for(ll i=0;i<m;i++)
+    {
+        ll u,v;
+        cin>>u>>v;
+        adj[u].push_back(v);
+        adj[v].push_back(u);
+    }
+    for(ll i=0;i<n;i++)
+    vis[i]=0;
+    vis[z]=1;
+    if(z==0)dfs(1);
+    else
+    dfs(0);
+    ll flag=0;
+    for(ll i=0;i<n;i++)
+    {
+        if(!vis[i])
+        {
+            flag=1;
+            break;
+        }
+    }
+    if(flag==0)
+    cout<<"yes\n";
+    else
+    cout<<"no\n";
+    
+}

data_structures/C++/detect_cycle_dfs.cpp

@@ -0,0 +1,51 @@
+#include<bits/stdc++.h>
+#define ll long long 
+#define pb push_back
+#define N 100000
+using namespace std;
+vector<ll>adj[N];   //storing the list
+vector<ll>vis(N);   
+bool cycle(ll curr,ll par)
+{
+    ll res=0;
+    vis[curr]=1;
+    for(auto neb:adj[curr])
+    {
+        if(neb==par)
+        continue;
+        if(vis[neb]==1)
+        return 1;
+        else
+        res|=cycle(neb,curr);
+    }
+    return res;
+    
+}
+int main()
+{
+    ll n,m;    //no.of nodes and no. of connection
+    cin>>n>>m;
+  
+    for(ll i=1;i<=m;i++)
+    {
+        ll u,v;
+        cin>>u>>v;
+        adj[u].pb(v);
+        adj[v].pb(u);
+        
+    }
+    for(ll i=1;i<=n;i++)
+    vis[i]=0;
+    ll flag=0;
+    for(ll i=1;i<=n;i++)
+    {
+        if(vis[i]==0)
+        {
+            flag|=cycle(i,0);
+        }
+    }
+    if(flag==1)
+    cout<<"YES\n";
+    else
+    cout<<"NO\n";
+}