Composite numbers k with no single digit factors whose factors are all substrings of k: Difference between revisions

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 =={{header|PARI/GP}}==
 <syntaxhighlight lang="PARI/GP">
+/* Returns a substring of str starting at s with length n */
-ssubstr(str,s=1,n=0)={
+ssubstr(str, s = 1, n = 0) = {
-my(vt=Vecsmall(str),ve,vr,vtn=#str,n1);
+    my(vt = Vecsmall(str), ve, vr, vtn = #str, n1);
-if(vtn==0,return(""));
-if(s<1||s>vtn,return(str));
+    if (vtn == 0, return(""));
+    if (s < 1 || s > vtn, return(str));
-n1=vtn-s+1; if(n==0,n=n1); if(n>n1,n=n1);
+    n1 = vtn - s + 1; if (n == 0, n = n1); if (n > n1, n = n1);
-ve=vector(n,z,z-1+s); vr=vecextract(vt,ve); return(Strchr(vr));
+    ve = vector(n, z, z - 1 + s); vr = vecextract(vt, ve); return(Strchr(vr));
 }
+/* Checks if subStr is a substring of mainStr */
 isSubstring(mainStr, subStr) = {
-  mainLen = #Vecsmall(mainStr);
+    mainLen = #Vecsmall(mainStr);
-  subLen = #Vecsmall(subStr);
+    subLen = #Vecsmall(subStr);
-  for (startPos=1, mainLen-subLen+1,
+    for (startPos = 1, mainLen - subLen + 1,
-    if (ssubstr(mainStr, startPos, subLen) == subStr,
+        if (ssubstr(mainStr, startPos, subLen) == subStr,
-      return (1); /* True, found the substring */
+            return(1); /* True: subStr found in mainStr */
-    )
+        )
-  );
+    );
-  return (0); /* False, substring not found */
+    return(0); /* False: subStr not found */
 }
+/* Determines if a number's factors, all > 9, are substrings of its decimal representation */
-\\ Determines if a number's factors, all > 9, are substrings of its decimal representation
 contains_its_prime_factors_all_over_9(n) = {
-    if(n < 10 || isprime(n), return(0)); \\ Early return if n < 10 or n is prime
+    if (n < 10 || isprime(n), return(0)); /* Skip if n < 10 or n is prime */
-    strn = Str(n); \\ Convert n to its string representation
+    strn = Str(n); /* Convert n to string */
-    pfacs = factor(n)[,1]; \\ Get the unique prime factors of n
+    pfacs = factor(n)[, 1]; /* Get unique prime factors of n */
-    \\print("n=" n ",pfacs=" pfacs);
+    for (i = 1, #pfacs,
+        if (pfacs[i] <= 9, return(0)); /* Skip factors ≤ 9 */
-    for(i=1, #pfacs,
-        if(pfacs[i] <= 9, return(0)); \\ Skip factors not greater than 9
+        if (!isSubstring(strn, Str(pfacs[i])), return(0)); /* Check if factor is a substring */
-        if(!isSubstring(strn, Str(pfacs[i])), return(0)); \\ Check if factor is not a substring
     );
-    return(1); \\ All conditions met
+    return(1); /* All checks passed */
 }
-\\ Main loop to find numbers meeting the criteria
+/* Main loop to find and print numbers meeting the criteria */
 {
-    found = 0; \\ Initialize counter
+    found = 0; /* Counter for numbers found */
-    for(n=0, 30*10^6, \\ Iterate from 0 to 30 million
+    for (n = 0, 30 * 10^6, /* Iterate from 0 to 30 million */
-        if(contains_its_prime_factors_all_over_9(n),
+        if (contains_its_prime_factors_all_over_9(n),
-            found += 1; \\ Increment counter if n meets the criteria
+            found += 1; /* Increment counter if n meets criteria */
-            print1(n, " "); \\ Print n followed by a space
+            print1(n, " "); /* Print n followed by a space */
-            if(found % 10 == 0, print("")); \\ Print a newline every 10 numbers
+            if (found % 10 == 0, print("")); /* Newline every 10 numbers */
-            if(found == 20, break); \\ Stop after finding 20 numbers
+            if (found == 20, break); /* Stop after finding 20 numbers */
         );
     );