hamilton

Author: sayedppqq

Graph/Hamilton Path.cpp

@@ -0,0 +1,99 @@
+#include<bits/stdc++.h>
+#include<ext/pb_ds/assoc_container.hpp>
+#include<ext/pb_ds/tree_policy.hpp>
+#define  FIO        ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
+#define  Fileio     freopen("output.txt","w",stdout);freopen("input.txt","r",stdin);
+#define  all(v)     v.begin(),v.end()
+#define  rall(v)    v.rbegin(),v.rend()
+#define  MEM(a,x)   memset(a,x,sizeof(a))
+#define  SZ(v)      v.size()
+#define  nl         "\n"
+#define  bug        cout<<"bug"<<nl;
+#define  pi         acos(-1.0)
+#define  ll     long long
+#define  pb     push_back
+#define  mp     make_pair
+#define  pii    pair< int,int >
+#define  pll    pair< ll,ll >
+#define  vii    vector< int >
+#define  vll    vector< ll >
+#define  vpi    vector< pii >
+#define  vpl    vector<pll>
+#define  MX     100005
+#define  EPS    1e-12
+#define  ss     second
+#define  ff     first
+using namespace std;
+using namespace __gnu_pbds;
+
+template<typename T>
+using ordered_set=tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;
+template<typename T>
+using ordered_multiset=tree<T, null_type, less_equal<T>, rb_tree_tag,tree_order_statistics_node_update>;
+
+inline ll powr(int a,int b){ll res=1;while(b){if(b&1) res*=a;a*=a;b/=2;}return res;}
+int cases=1;
+
+#ifdef ppqq
+     #define debug(...) __f(#__VA_ARGS__, __VA_ARGS__)
+    template < typename Arg1 >
+    void __f(const char* name, Arg1&& arg1){
+        cerr << name << " is " << arg1 << std::endl;
+    }
+    template < typename Arg1, typename... Args>
+    void __f(const char* names, Arg1&& arg1, Args&&... args){
+        const char* comma = strchr(names+1, ',');
+        cerr.write(names, comma - names) << " is " << arg1 <<"  ";
+        __f(comma+1, args...);
+    }
+#else
+    #define debug(...)
+#endif
+
+///******************************************START******************************************
+vii adj[MX];
+const ll MOD = (ll) 1e9 + 7;
+void countHamiltonPath(int n)
+{
+    //Ref : https://cses.fi/problemset/task/1690
+
+    vector<vector<long long>> dp(n+2,vector<long long>((1<<n)+5,0));
+    dp[0][1]=1;
+
+    for(int i=2;i<(1<<n);i++)
+    {
+        //only taking subsets which starts with 0
+        if((i & (1<<0))==0) continue;
+
+        for(int start=0;start<n;start++)
+        {
+            if((i & (1<<start))==0) continue;
+
+            for(auto endd: adj[start])
+            {
+                int prev=i^(1<<endd);
+                if(i & (1<<endd))
+                {
+                    dp[endd][i]+=dp[start][prev];
+                    dp[endd][i]%=MOD;
+                }
+            }
+        }
+    }
+    cout<<dp[n-1][(1<<n)-1];
+}
+int main()
+{
+    FIO;
+    int n,m;
+    cin>>n>>m;
+    for(int i=0;i<m;i++)
+    {
+        int u,v;
+        cin>>u>>v;
+        u--;v--;
+        adj[u].pb(v);
+        adj[v].pb(u);
+    }
+    countHamiltonPath(n);
+}