Accelerated C++ 学习笔记及题解----第二章

本节主要讲解的是:

while语句

if语句

for语句

逻辑运算符.

本节设计的新类型有:

bool   布尔值

unsigned 非负整数

short 至少16位整数

long

size_t 无符号整数类型,可以保存任何对象的长度

string::size_type 无符号整数类型,可以存储任意字符串的长度

书中的源代码:frame.cpp

#include <iostream>
#include <string>

// say what standard-library names we use
using namespace std;


int main()
{
	// ask for the person's name
	cout << "Please enter your first name: ";

	// read the name
	string name;
	cin >> name;

	// build the message that we intend to write
	const string greeting = "Hello, " + name + "!";

	// the number of blanks surrounding the greeting
	const int pad = 1;

	// the number of rows and columns to write
	const int rows = pad * 2 + 3;
	const string::size_type cols = greeting.size() + pad * 2 + 2;

	// write a blank line to separate the output from the input
	cout << endl;

	// write `rows' rows of output
	// invariant: we have written `r' rows so far
	for (int r = 0; r != rows; ++r) {

		string::size_type c = 0;

		// invariant: we have written `c' characters so far in the current row
		while (c != cols) {

			// is it time to write the greeting?
			if (r == pad + 1 && c == pad + 1) {
				cout << greeting;
				c += greeting.size();
			} else {

				// are we on the border?
				if (r == 0 || r == rows - 1 ||
				    c == 0 || c == cols - 1)
					cout << "*";
				else
					cout << " ";
				++c;
			}
		}

		cout << endl;
	}

	return 0;
}

题解:

2-1

将上面的代码pad改为0

2-2

#include <iostream>
#include <string>
// say what standard-library names we use
using std::cin; using std::endl;
using std::cout; using std::string;
int main()
{
	// ask for the person's name
	cout << "Please enter your first name: ";
	// read the name
	string name;
	cin >> name;
	// build the message that we intend to write
	const string greeting = "Hello, " + name + "!";
	// the number of blanks surrounding the greeting
	const int h_pad = 1;
	const int v_pad = 2;
	// the number of rows and columns to write
	const int rows = v_pad * 2 + 3;
	const string::size_type cols = greeting.size() + h_pad * 2 + 2;
	// write a blank line to separate the output from the input
	cout << endl;
	// write `rows' rows of output
	// invariant: we have written `r' rows so far
	for (int r = 0; r != rows; ++r)
	{
		string::size_type c = 0;
		// invariant: we have written `c' characters so far in the current row
		while (c != cols)
		{
			// is it time to write the greeting?
			if (r == v_pad + 1 && c == h_pad + 1)
			{
				cout << greeting;
				c += greeting.size();
			} else 
			{
				// are we on the border?
				if (r == 0 || r == rows - 1 ||
					c == 0 || c == cols - 1)
					cout << "*";
				else
					cout << " ";
				++c;
			}
		}
		cout << endl;
	}
	return 0;
}

2-3

#include <iostream>
#include <string>

// say what standard-library names we use
using namespace std;


int main()
{
	// ask for the person's name
	cout << "Please enter your first name: ";

	// read the name
	string name;
	cin >> name;

	// build the message that we intend to write
	const string greeting = "Hello, " + name + "!";

	// the number of blanks surrounding the greeting
	int pad ;
    cout << "Please input the number of the space :" ;
    cin >> pad;
	// the number of rows and columns to write
	const int rows = pad * 2 + 3;
	const string::size_type cols = greeting.size() + pad * 2 + 2;

	// write a blank line to separate the output from the input
	cout << endl;

	// write `rows' rows of output
	// invariant: we have written `r' rows so far
	for (int r = 0; r != rows; ++r) {

		string::size_type c = 0;

		// invariant: we have written `c' characters so far in the current row
		while (c != cols) {

			// is it time to write the greeting?
			if (r == pad + 1 && c == pad + 1) {
				cout << greeting;
				c += greeting.size();
			} else {

				// are we on the border?
				if (r == 0 || r == rows - 1 ||
				    c == 0 || c == cols - 1)
					cout << "*";
				else
					cout << " ";
				++c;
			}
		}

		cout << endl;
	}

	return 0;
}

2-4

#include <iostream>
#include <string>
// say what standard-library names we use
using std::cin; using std::endl;
using std::cout; using std::string;

int main() 
{
	// ask for the person's name
	cout << "Please enter your first name: ";
	// read the name
	string name;
	cin >> name;
	// build the message that we intend to write
	const string greeting = "Hello, " + name + "!";
	// the number of blanks surrounding the greeting
	const int pad = 1;
	// the number of rows and columns to write
	const int rows = pad * 2 + 3;
	const string::size_type cols = greeting.size() + pad * 2 + 2;
	const string spaces = string(greeting.size() + pad * 2, ' ');
	// write a blank line to separate the output from the input
	cout << endl;
	// write `rows' rows of output
	// invariant: we have written `r' rows so far
	for (int r = 0; r != rows; ++r)
	{
		string::size_type c = 0;
		// invariant: we have written `c' characters so far in the current row
		while (c != cols) {
			// is it time to write the greeting?
			if (r == pad + 1 && c == pad + 1)
			{
				cout << greeting;
				c += greeting.size();
			} else 
			{
				// are we on the border?
				if (r == 0 || r == rows - 1 ||
					c == 0 || c == cols - 1) 
				{
					cout << "*";
					++c;
				} else if (r == pad + 1) 
				{
					cout << " ";
					++c;
				} else 
				{
					cout << spaces;
					c += spaces.size();
				}
			}
		}
		cout << endl;
	}
	return 0;
}

2-5

#include <iostream>

using namespace std;

int main()
{
    int length;
    cout << "This program is intend to print a 正方形 and 三角形 :" << endl;
    cout << "Please input the length of border: " ;
    cin >> length;
    // print the 正方形
    for (int i = 0; i<length; i++ )
    {
        for(int j = 0; j < length; j++)
        {
            if(i ==0 || i == length-1)
            {
                cout << "*" ;
            }
            else
                if(j == 0 || j == length -1)
                    cout << "*";
                else cout << " ";
        }
        cout << endl;
    }
    // print 三角形
    ..............such as....
    return 0;
}

............余下省略,就是联系循环和控制流的....