fix exercise 16.3 16.4

Add a test for exercise 16.3.
A better solution for exercise 16.4.

ch16/ex16.1.2.3/main.cpp

@@ -25,6 +25,11 @@
 //!
 
 #include <iostream>
+using std::cout;
+using std::endl;
+
+#include<vector>
+using std::vector;
 
 class Sales_data
 {
@@ -41,6 +46,12 @@ int compare(const T& lhs, const T& rhs)
 
 int main()
 {
+    //! Test compare function
+    cout << compare(1, 0) << endl;
+
+    vector<int> vec1{1, 2, 3}, vec2{4, 5, 6};
+    cout << compare(vec1, vec2) << endl;
+
     return 0;
 }
 

ch16/ex16.4/main.cpp

@@ -22,13 +22,9 @@
 template<typename iteratorT, typename valueT>
 iteratorT find(const iteratorT& first, const iteratorT& last,const valueT& value )
 {
-    if (first == last)  return last;
-    else
-    {
-        for (auto it = first; it != last; ++it)
-            if(*it == value)    return it;
-        return last;
-    }
+    auto iter = first;
+    while(iter != last && *iter != value) ++iter;
+    return iter;
 }
 
 int main()