Middle three digits: Difference between revisions

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 	return 0;
 }</lang>
+=={{header|C++}}==
+<lang cpp>#include <iostream>
+#include <sstream>
+#include <string>
+// @author Martin Ettl
+// @date   2013-02-04
+/**
+ * Convert variables of type T to std::string
+ *
+ *
+ * @param d --> digit of type T
+ *
+ * @return <-- the corresponding string value
+ */
+template <typename T> const std::string toString(const T &d)
+{
+    std::ostringstream result;
+    result << d;
+    return result.str();
+}
+/**
+ * Determine the middle n digits of the integer. If it is not possible to determine the
+ * the middle n digits, an empty string is provided.
+ *
+ * @param iDigit --> The digit to test
+ * @param n      --> The number of digits inbetween
+ *
+ * @return <-- the middle three digits
+ */
+std::string strMiddleNDigits(int iDigit, const int &n)
+{
+    // is negative: --> convert to a positive number
+    if(iDigit<0)
+    {
+        iDigit*=-1;
+    }
+    // convert to string
+    std::string strNumber (toString(iDigit));
+    size_t len(strNumber.length());
+    if( (len < n) || (len % 2 == 0) )
+    {
+        return "";
+    }
+    size_t mid(len/2);
+    return strNumber.substr(mid-n/2, n);
+}
+/**
+ * Determine the middle three digits of the integer. If it is not possible to determine the
+ * the middle three digits, an empty string is provided.
+ *
+ * @param iDigit --> The digit to test
+ *
+ * @return <-- the middle three digits
+ */
+std::string strMiddleThreeDigits(int iDigit)
+{
+    return strMiddleNDigits(iDigit,3);
+}
+int main()
+{
+    const int iPassing[] = {123, 12345, 1234567, 987654321, 10001, -10001,
+                            -123, -100, 100, -12345
+                           };
+    for(unsigned int ui = 0; ui < 10; ++ui)
+    {
+        std::cout << "strMiddleThreeDigits("<< iPassing[ui] <<"): "
+                  << strMiddleThreeDigits(iPassing[ui])<< "\n";
+    }
+    const int iFailing[] = {1, 2, -1, -10, 2002, -2002, 0};
+    for(unsigned int ui = 0; ui < 7; ++ui)
+    {
+        std::string strResult = strMiddleThreeDigits(iFailing[ui]);
+        std::cout << "strMiddleThreeDigits("<< iFailing[ui] <<"): "
+                  << (strResult.empty()?"Need odd and >= 3 digits":strResult)
+                  << "\n";
+    }
+    return 0;
+}
+</lang>
+{{out}}
+<pre>strMiddleThreeDigits(123): 123
+strMiddleThreeDigits(12345): 234
+strMiddleThreeDigits(1234567): 345
+strMiddleThreeDigits(987654321): 654
+strMiddleThreeDigits(10001): 000
+strMiddleThreeDigits(-10001): 000
+strMiddleThreeDigits(-123): 123
+strMiddleThreeDigits(-100): 100
+strMiddleThreeDigits(100): 100
+strMiddleThreeDigits(-12345): 234
+strMiddleThreeDigits(1): Need odd and >= 3 digits
+strMiddleThreeDigits(2): Need odd and >= 3 digits
+strMiddleThreeDigits(-1): Need odd and >= 3 digits
+strMiddleThreeDigits(-10): Need odd and >= 3 digits
+strMiddleThreeDigits(2002): Need odd and >= 3 digits
+strMiddleThreeDigits(-2002): Need odd and >= 3 digits
+strMiddleThreeDigits(0): Need odd and >= 3 digits</pre>
 =={{header|D}}==