Update euler-0038.cpp

euler-0038.cpp

@@ -41,84 +41,46 @@
 // The result may have either 8 or 9 digits and there is an upper limit for the start value.
 
 #include <iostream>
+#include <string>
+#include <vector>
+#include <algorithm>
+
+bool isPandigital(const std::string& s, int K) {
+    if (s.length() != K) return false;
+    std::vector<bool> seen(K + 1, false); // index 0 to K
+
+    for (char c : s) {
+        int d = c - '0';
+        if (d == 0 || d > K || seen[d]) return false;
+        seen[d] = true;
+    }
+    return true;
+}
 
-int main()
-{
-  unsigned int maxFactor, maxDigit;  // 10000 and 9 for the original problem
-  std::cin >> maxFactor >> maxDigit;
-
-  // bitmask if all digits are used
-  unsigned int bitsAll = 0;
-  for (unsigned int i = 1; i <= maxDigit; i++)
-    bitsAll |= 1 << i;
-
-#define ORIGINAL
-#ifdef ORIGINAL
-  // largest pandigital number found so far
-  unsigned int largest = 0;
-#endif
-
-  // try all numbers
-  for (unsigned int i = 2; i <= maxFactor; i++)
-  {
-    // the whole pandigital number
-    unsigned int pandigital = 0;
-
-    // multiply i by 1,2,3,...
-    unsigned int multiplier = 1;
-
-    // bitmask of used digits (nth bit is set if pandigital contains digit n)
-    unsigned int bitsUsed   = 0;
-
-    while (bitsUsed < bitsAll)
-    {
-      // next step
-      unsigned int product = i * multiplier;
+int main() {
+    int N, K;
+    std::cin >> N >> K;
 
-      // extract right-most digit
-      while (product > 0)
-      {
-        // extract right-most digit
-        unsigned int digit = product % 10;
-        // remove it
-        product    /= 10;
+    std::vector<int> results;
 
-        // make room to add i*multiplier lateron
-        pandigital *= 10;
+    for (int M = 2; M < N; ++M) {
+        std::string concat = "";
+        int multiplier = 1;
 
-        // remember all digits we used
-        unsigned int bitMask = 1 << digit;
-        // we already had this digit ?
-        if (digit == 0 || (bitsUsed & bitMask) != 0)
-        {
-          bitsUsed = bitsAll + 1; // set to an invalid value
-          break;
+        while ((int)concat.length() < K) {
+            concat += std::to_string(M * multiplier);
+            ++multiplier;
         }
 
-        // mark current digit as "used"
-        bitsUsed |= bitMask;
-      }
-
-      // keep going in the sequence
-      pandigital += i * multiplier;
-      multiplier++;
+        if (isPandigital(concat, K)) {
+            results.push_back(M);
+        }
     }
 
-    // enough digits generated ?
-    if (bitsUsed == bitsAll)
-    {
-#ifdef ORIGINAL
-      if (largest < pandigital)
-        largest = pandigital;
-#else
-      std::cout << i << std::endl;
-#endif
+    for (int r : results) {
+        std::cout << r << std::endl;
     }
-  }
-
-#ifdef ORIGINAL
-  std::cout << largest << std::endl;
-#endif
 
-  return 0;
+    return 0;
 }
+