added ex3.1~3.5

ch03/ex3_1a.cpp

@@ -0,0 +1,20 @@
+// use `using` for 1.4.1
+
+#include <iostream>
+
+using std::cin;
+using std::cout;
+using std::endl;
+
+int main()
+{
+  int sum = 0, val = 1;
+  // keep executing the while as long as val is less than or equal to 10
+  while (val <= 10)
+  {
+    sum += val;
+    ++val;
+  }
+  cout << "Sum of 1 to 10 inclusive is " << sum << endl;
+  return 0;
+}

ch03/ex3_1b.cpp

@@ -0,0 +1,48 @@
+#include <iostream>
+#include <string>
+#include "../ch02/Sales_data.h"
+
+using std::cin;
+using std::cout;
+using std::endl;
+using std::cerr;
+
+int main()
+{
+  Sales_data data1, data2;
+
+  // code to read into data1 and data2
+  double price = 0;  // price per book, used to calculate total revenue
+
+  // read the first transactions: ISBN, number of books sold, price per book 
+  cin >> data1.bookNo >> data1.units_sold >> price;
+  // calculate total revenue from price and units_sold
+  data1.revenue = data1.units_sold * price;
+
+  // read the second transaction
+  cin >> data2.bookNo >> data2.units_sold >> price;
+  data2.revenue = data2.units_sold * price;
+
+  // code to check whether data1 and data2 have the same ISBN
+  //        and if so print the sum of data1 and data2
+  if (data1.bookNo == data2.bookNo)
+  {
+    unsigned totalCnt = data1.units_sold + data2.units_sold;
+    double totalRevenue = data1.revenue + data2.revenue;
+
+    // print: ISBN, total sold, total revenue, average price per book
+    cout << data1.bookNo << " " << totalCnt 
+         << " " << totalRevenue << " ";
+    if (totalCnt != 0)
+      cout << totalRevenue/totalCnt << endl;
+    else
+      cout  << "(no sales)" << endl;
+
+    return 0;  // indicate success
+  }
+  else
+  {  // transactions weren't for the same ISBN
+    cerr << "Data must refer to the same ISBN" << endl;
+    return -1; // indicate failure
+  }
+}

ch03/ex3_2a.cpp

@@ -0,0 +1,18 @@
+// read the standard input a line at a time.
+#include <iostream>
+#include <string>
+
+using std::string;
+using std::cin;
+using std::cout;
+using std::endl;
+using std::getline;
+
+int main()
+{
+  string input;
+  while (getline(cin, input))
+    cout << input << endl;
+
+  return 0;
+}

ch03/ex3_2b.cpp

@@ -0,0 +1,17 @@
+// read the standard input a word at a time
+#include <iostream>
+#include <string>
+
+using std::string;
+using std::cin;
+using std::cout;
+using std::endl;
+
+int main()
+{
+  string word;
+  while (cin >> word)
+    cout << word << endl;
+
+  return 0;
+}

ch03/ex3_4a.cpp

@@ -0,0 +1,23 @@
+// read two strings and report whether the strings are equal
+// If not, report which of the two is larger.
+#include <iostream>
+#include <string>
+
+using std::string;
+using std::cin;
+using std::cout;
+using std::endl;
+
+int main()
+{
+  string str1, str2;
+  while (cin >> str1 >> str2)
+  {
+    if (str1 == str2)
+      cout << "The two strings are equal." << endl;
+    else
+      cout << "The larger string is " << ((str1 > str2) ? str1 : str2);
+  }
+
+  return 0;
+}

ch03/ex3_4b.cpp

@@ -0,0 +1,23 @@
+// read two strings and report whether the strings have the same length
+// If not, report which is longer
+#include <iostream>
+#include <string>
+
+using std::string;
+using std::cin;
+using std::cout;
+using std::endl;
+
+int main()
+{
+  string str1, str2;
+  while (cin >> str1 >> str2)
+  {
+    if (str1.size() == str2.size())
+      cout << "The two strings have the same length." << endl;
+    else
+      cout << "The longer string is " << ((str1.size() > str2.size()) ? str1 : str2);
+  }
+
+  return 0;
+}

ch03/ex3_5a.cpp

@@ -0,0 +1,23 @@
+//read strings from the standard input, concatenating what is read into one large string. 
+//Print the concatenated string.
+#include <iostream>
+#include <string>
+
+using std::string;
+using std::cin;
+using std::cout;
+using std::endl;
+
+int main()
+{
+  string largeStr;
+  string str;
+  while (cin >> str)
+  {
+    largeStr += str;
+  }
+
+  cout << "The concatenated string is " << largeStr << endl;
+
+  return 0;
+}

ch03/ex3_5b.cpp

@@ -0,0 +1,25 @@
+//separate adjacent input strings by a space.
+#include <iostream>
+#include <string>
+
+using std::string;
+using std::cin;
+using std::cout;
+using std::endl;
+
+int main()
+{
+  string largeStr;
+  string str;
+  while (cin >> str)
+  {
+    if (largeStr.empty())
+      largeStr += str;
+    else
+      largeStr += " " + str;
+  }
+
+  cout << "The concatenated string is " << largeStr << endl;
+
+  return 0;
+}

docs/ch03/ex3.3.md

@@ -0,0 +1 @@
+##Exercise 3.3>Explain how whitespace characters are handled in the stringinput operator and in the getline function.The `getline` function takes an input stream and a string.This function reads the given stream up to and including the first newline and stores what it read—not includingthe newline—in its string argument.After getline sees a newline, even if it is the first character in the input,it stops reading and returns.If the first character in the input is a newline,then the resulting string is the empty string.`getline` function whitespace handling,do not ignore the beginning of the line blank characters read charactersuntil it encounters a line break,read to termination and discard newline(line breaks removed from the input stream  but is not stored in the string object).[Read more](http://www.cplusplus.com/reference/string/string/getline/)

docs/index.md

@@ -26,6 +26,11 @@ C++ Primer 5th Answer Note
     - [Exercise 2.36 ~ 2.38](/Cpp-Primer/ch02/ex2.36_2.38)
     - [Exercise 2.39 ~ 2.42](/Cpp-Primer/ch02/ex2.39_2.42)
   - Chapter 3. Strings, Vectors, and Arrays
+    - Exercise [3.1a](https://github.com/pezy/Cpp-Primer/blob/master/ch03/ex3_1a.cpp)&[3.1b](https://github.com/pezy/Cpp-Primer/blob/master/ch03/ex3_1b.cpp)
+    - Exercise [3.2a](https://github.com/pezy/Cpp-Primer/blob/master/ch03/ex3_2a.cpp)&[3.2b](https://github.com/pezy/Cpp-Primer/blob/master/ch03/ex3_2b.cpp) |
+    [3.3](/Cpp-Primer/ch03/ex3.3) |
+    [3.4a](https://github.com/pezy/Cpp-Primer/blob/master/ch03/ex3_4a.cpp)&[3.4b](https://github.com/pezy/Cpp-Primer/blob/master/ch03/ex3_4b.cpp) |
+    [3.5a](https://github.com/pezy/Cpp-Primer/blob/master/ch03/ex3_5a.cpp)&[3.5b](https://github.com/pezy/Cpp-Primer/blob/master/ch03/ex3_5b.cpp)
   - Chapter 4. Expressions
   - Chapter 5. Statements
   - Chapter 6. Functions