Merge pull request pezy#91 from sanerror/master

Update ex12_23.cpp

ch12/ex12_23.cpp

@@ -3,6 +3,7 @@
 //  Exercise 12.23
 //
 //  Created by pezy on 12/30/14.
+//  Updated by sanerror on 11/9/16.
 //  Copyright (c) 2014 pezy. All rights reserved.
 //
 //  Write a program to concatenate two string literals, putting the result in a
@@ -12,18 +13,23 @@
 
 #include <iostream>
 #include <string>
-#include <string.h>
+#include <cstring>
 
-int main()
-{
-    // dynamically allocated array of char
-    char* concatenate_string = new char[255]();
-    strcat(concatenate_string, "hello ");
-    strcat(concatenate_string, "world");
-    std::cout << concatenate_string << std::endl;
-    delete[] concatenate_string;
+int main() {
+	const char *c1 = "Hello ";
+	const char *c2 = "World";
+	unsigned len = strlen(c1) + strlen(c2) + 1;
+	char *r = new char[len]();
+	strcat_s(r, len, c1);
+	strcat_s(r, len, c2);
+	std::cout << r << std::endl;
 
-    // std::string
-    std::string str1{"hello "}, str2{"world"};
-    std::cout << str1 + str2 << std::endl;
+	std::string s1 = "Hello ";
+	std::string s2 = "World";
+	strcpy_s(r, len, (s1 + s2).c_str());
+	std::cout << r << std::endl;
+
+	delete[] r;
+
+	return 0;
 }