D - Required Length

https://codeforces.com/contest/1681/submission/158228515

Codeforces/1681/D/D.cpp

@@ -0,0 +1,53 @@
+#pragma GCC optimize("Ofast")
+
+#include <cmath>
+#include <iostream>
+#include <map>
+#include <string>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+long long n, x;
+std::map<long long, int> map;
+
+inline int len(long long x) {
+    if (x == 0) return 0;
+
+    return (int)log10(x) + 1;
+}
+
+int dfs(long long x) {
+    if (map.count(x)) return map[x];
+
+    map[x] = 0x3f3f3f3f;
+
+    std::vector<int> a;
+    long long t = x;
+    while (t) {
+        a.push_back(t % 10);
+        t /= 10;
+    }
+
+    if (a.size() == n) return map[x] = 0;
+
+    for (int i : a) {
+        map[x] = std::min(map[x], dfs(x * i) + 1);
+    }
+
+    return map[x];
+}
+
+signed main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> n >> x;
+
+    int ans = dfs(x);
+
+    cout << (ans == 0x3f3f3f3f ? -1 : ans) << endl;
+
+    return 0;
+}