chore: solved hard day 3 task

Hard/Day3/Solution.cpp

@@ -0,0 +1,124 @@
+// #include <bits/stdc++.h>
+// using namespace std;
+// #define int long long int
+// #define ff(n) for(int i=0;i<n;i++)
+// #define pb push_back
+// #define cy {cout<<"YES\n"; return;}
+// #define cn {cout<<"NO"<<endl; return;}
+// #define c0 {cout<<0<<endl; return;}
+// #define c1 {cout<<1<<endl; return;}
+// #define c01 {cout<<-1<<endl; return;}
+// #define el {cout<<endl;}
+// #define all(r) r.begin(),r.end()
+// #define ffj(n) for(int j=0;j<n;j++)
+// #define vp vector<pair <int,int>>
+// #define mapp map<int,int> 
+// #define vi vector<int>
+// #define count int cnt=0;
+// #define array {int n; cin>>n;int a[n];ff(n) cin>>a[i];}
+// #define ipn {int n; cin>>n;}
+
+
+
+
+
+// const int N = 1e5 + 10;
+// const int mod = 1e9 + 7;
+
+// int power(int a, int b) {
+//     int res = 1;
+//     while (b > 0) {
+//         if (b & 1)
+//             res = (res * a)%mod;
+//         a = (a * a)%mod;
+//         (b >>= 1)%mod;
+//     }
+//     return res%mod;
+// }
+
+// void solve()
+// { 
+//     int n;
+// 		cin>>n;
+// 		int k;
+// 		cin>>k;
+// 		int chk = power(n,k)%mod;
+// 		int ans = chk%mod;
+// 		cout<<ans<<endl;
+// }
+
+
+
+
+
+
+// signed main() 
+// {
+// 	int t;
+// 	cin>>t;
+//     // cout<<t<<endl;
+// 	while(t--)
+//     {
+//         solve();   
+//     }
+// 	return 0;
+// }
+
+
+
+
+  #include<bits/stdc++.h>
+
+using namespace std;
+
+const int mod = 1e9 + 7;
+const int N = 2e6 + 10;
+
+int fact[N], infact[N];
+
+int qmi(int a, int b)
+{
+	int res = 1;
+	while(b)
+	{
+		if(b & 1)	res = (int)res * a % mod;
+		a = (int)a * a % mod;
+		b >>= 1;
+	}
+	return res;
+}
+
+void init()
+{
+	fact[0] = 1, infact[0] = 1;
+    for(int i = 1; i < N; ++i)
+    {
+        fact[i] = (int)fact[i - 1] * i % mod;
+        infact[i] = (int)infact[i - 1] * qmi(i, mod - 2) % mod;
+    }
+}
+
+int C(int a, int b)
+{
+	return (int)fact[a] * infact[b] % mod * infact[a - b] % mod;
+}
+
+int main()
+{
+	int k;
+	string s;
+	cin >> k >> s;
+
+	int len = s.length();
+	int n = k + len;
+	init();						
+
+	int ans = 0;
+	for(int i = len; i <= n; i++)
+	{
+		int t = (int)C(i - 1, len - 1) * qmi(25, i - len) % mod * qmi(26, n - i) % mod;
+		ans = (ans % mod + t % mod) % mod;
+	}
+	cout << ans << endl;
+	return 0;
+}