done 3 sorting problems

CSES - CSES Problem Set/Introducotry_Problems/Bit_Strings.cpp

@@ -0,0 +1,19 @@
+//  Bit Strings
+
+#include<bits/stdc++.h>
+
+using namespace std;
+using ll = long long;
+ll MOD = 1e9 + 7;
+
+int main() {
+    int n; cin >> n;
+    ll ans = 1;
+    for (int i{}; i < n; i++) {
+        ans *= 2;
+        ans %= MOD;
+    }
+    ans %= MOD;
+    cout << ans;
+    return 0;
+}