Adding input validation (C, C++, C#, Java)

sieve-of-eratosthenes/c/sieve_c.c

@@ -1,8 +1,9 @@
 #include <math.h>
 #include <stdio.h>
-#include <stdlib.h> 
+#include <stdlib.h>
 #include <time.h>
 #include <string.h>
+#include <ctype.h>
 
 int main(int argc, char const** argv)
 {
@@ -11,6 +12,14 @@ int main(int argc, char const** argv)
         return 1;
     }
 
+    for (int pos = 0; pos < strlen(argv[1]); pos++)
+    {
+        if(!isdigit(argv[1][pos]))
+        {
+          return 1;
+        }
+    }
+
     unsigned int max = atoi(argv[1]);
     unsigned int arraySize = max * sizeof(unsigned char);
     clock_t begin = clock();
@@ -38,7 +47,7 @@ int main(int argc, char const** argv)
     }
 
     clock_t end = clock();
-    float duration = (((float)end - (float)begin) / 1000000.0F ) * 1000;   
+    float duration = (((float)end - (float)begin) / 1000000.0F ) * 1000;
     printf("Number of primes: %i\n", numPrimes);
     printf("Execution time: %fms\n", duration);
 

sieve-of-eratosthenes/cpp/sieve_cpp.cpp

@@ -3,16 +3,25 @@
 #include <cstdlib>
 #include <math.h>
 #include <stdio.h>
+#include <ctype.h>
 #include <chrono>
 using namespace std;
 
 int main(int argc, char const** argv)
 {
-    if (argc != 2)
+    if(argc != 2)
     {
         return 1;
     }
 
+    for (int pos = 0; pos < strlen(argv[1]); pos++)
+    {
+        if(!isdigit(argv[1][pos]))
+        {
+          return 1;
+        }
+    }
+
     int max = atoi(argv[1]);
 
     auto begin = chrono::high_resolution_clock::now();

sieve-of-eratosthenes/csharp/sieve_csharp.cs

@@ -3,10 +3,8 @@
 
 public class PrimeSieve
 {
-    public static void Main(string[] args)
+    static void primes(int max)
     {
-        var max = int.Parse(args[0]);
-
         var primes = new bool[max];
 
         primes[0] = true;
@@ -34,5 +32,23 @@ public static void Main(string[] args)
         sw.Stop();
         Console.WriteLine("Number of primes: {0}", foundPrimes);
         Console.WriteLine("Execution time: {0}ms", sw.ElapsedMilliseconds);
+    }
+
+    public static int Main(string[] args)
+    {
+        try {
+            var max = int.Parse(args[0]);
+            primes(max);
+            return 0;
+        }
+        catch (FormatException) {
+            return 1;
+        }
+        catch (OverflowException) {
+            return 1;
+        }
+        catch (IndexOutOfRangeException) {
+            return 1;
         }
+    }
 }

sieve-of-eratosthenes/java/sieve_java.java

@@ -4,11 +4,8 @@
 
 public class sieve_java
 {
-
-    public static void main(String[] args)
+    static void primes(int max)
     {
-
-        int max = Integer.parseInt(args[0]);
         DecimalFormat df = new DecimalFormat("#.###"); df.setRoundingMode(RoundingMode.CEILING);
         long startTime = System.nanoTime();
 
@@ -42,4 +39,16 @@ public static void main(String[] args)
         System.out.println("Execution time: " +
           df.format((endTime - startTime)/1e6) + "ms");
     }
+
+    public static void main(String[] args)
+    {
+
+        try {
+            int max = Integer.parseInt(args[0]);
+            primes(max);
+        }
+        catch(NumberFormatException | ArrayIndexOutOfBoundsException e) {
+            System.exit(1);
+        }
+    }
 }