Added INOI 2020 problem

Author: Idkwhoami42

Dynamic Programming/(CODECHEF) INOI2002 - 3xN Tiling.cpp

@@ -0,0 +1,37 @@
+#include<bits/stdc++.h>
+using namespace std;
+#define ll long long
+const ll mod = 1e9+7, N = 1e6+7;
+int main()
+{
+    ll t;
+    cin>>t;
+    while(t--){
+        ll k, n;
+        cin>>k>>n;
+        if(k == 1){
+            cout<<(n%3==0?1:0)<<endl;
+        }
+        else if(k == 2){
+            vector<ll> dp(n+5, 0);
+            dp[2] = 1;
+            dp[3] = 1;
+            for(ll i = 4;i<=n;i++)dp[i] = (dp[i-3]+dp[i-2])%mod;
+            cout<<dp[n]<<endl;
+        }
+        else{
+            vector<ll> dp(n+5, 0), dp2(n+5, 0), dp3(n+5, 0);
+            dp[1] = dp[2] = dp[3] = 1;
+            dp[3]++;
+            dp3[3] = 1;
+
+            for(int i = 4;i<=n;i++){
+                dp[i] = (dp[i-3]%mod + dp[i-1]%mod + (dp2[i  -2]*2)%mod)%mod; 
+                dp3[i] = (dp[i-3] + dp3[i-3])%mod ;
+                dp2[i] = (dp2[i-3] + dp3[i-1])%mod;
+            
+            }
+            cout<<dp[n]%mod<<endl;
+        }
+    }
+}