Create Round Trip 2.cpp

Author: ShreyanshMehta

Diff for: Round Trip 2.cpp

@@ -0,0 +1,90 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+#define   fi(a,b) for(int i=a;i<b;i++)
+#define   fj(a,b) for(int j=a;j<b;j++)
+#define   ff first
+#define   ss second
+#define   ll long long
+#define   ld long double
+#define   ull unsigned long long
+#define   bp(x) __builtin_popcount(x)
+#define   pr(x) for(auto it: x) cout<<it<<" "; cout<<endl;
+#define   getMax(x) max_element(x.begin(),x.end())
+#define   getMin(x) min_element(x.begin(),x.end())
+#define   endl "\n"
+typedef   vector<int> vi;
+typedef   vector< pair<int,int> > vii;
+typedef   vector<long long> vl;
+typedef   pair<int,int> pii;
+typedef   pair<ll,ll> pll;
+typedef   vector< pair<ll,ll> > vll;
+//int dx[]={1,0,-1,0};
+//int dy[]={0,1,0,-1};
+//int dx[]={-1,0,1,1,1,0,-1,-1};
+//int dy[]={-1,-1,-1,0,1,1,1,0};
+
+const int N = 1e5+10;
+vi adj[N];
+vi parent(N);
+vi color(N);
+ 
+int start_node=-1, end_node=-1;
+ 
+bool dfs(int node,int pre){
+    color[node] = 1;
+    for(auto it: adj[node]){
+        // if(it==pre) continue;
+        if(color[it]==0){
+            parent[it] = node;
+            if(dfs(it, node)) return 1;
+        }
+        else if(color[it]==1){
+            start_node = it;
+            end_node = node;
+            return 1;
+        }
+    }
+    color[node] = 2;
+    return 0;
+}
+ 
+void nikal_pehli_fursat_mai(){
+    int n, m;
+    cin>>n>>m;
+    fi(0, m){
+        int u, v;
+        cin>>u>>v;
+        adj[u].push_back(v);
+    }
+    vi ans;
+ 
+    fi(1, n+1){
+        if(color[i]==0 and dfs(i, 0) and start_node!=-1){
+            ans.push_back(start_node);
+            for(int v = end_node; v != start_node; v = parent[v] ){
+                ans.push_back(v);
+            }
+            ans.push_back(start_node);
+            reverse(ans.begin(), ans.end());
+            cout<<ans.size()<<endl;
+            pr(ans);
+            return;
+        }
+    }
+    cout<<"IMPOSSIBLE"<<endl;
+}
+
+int main(){
+    #ifndef ONLINE_JUDGE
+    freopen("input.txt", "r", stdin);
+    freopen("output.txt", "w", stdout);
+    #endif
+    ios::sync_with_stdio(0);
+    cin.tie(0);
+    int tc=1; 
+    // cin>>tc;
+    while(tc--){
+        nikal_pehli_fursat_mai();
+    }
+}