new: CSES Introductory problems

solutions/CSES/Introductory Problems/2431 - Digit Queries.cpp

@@ -0,0 +1,25 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+void solve() {
+   long long k;
+   cin >> k;
+   k--;
+   long long cur = 9, d = 1;
+   while (k >= d * cur) k -= d * cur, d++, cur *= 10;
+   long long pref = cur / 9, offset = k / d;
+   long long nb = offset + pref;
+   long long pos = d - (k % d) - 1;
+   while (pos) nb /= 10, pos--;
+   cout << nb % 10 << "\n";
+}
+
+int main() {
+   ios::sync_with_stdio(false);
+   cin.tie(0);
+   cout.tie(0);
+
+   int t = 1;
+   cin >> t;
+   while (t--) solve();
+}