1.要输出bool，要设置标记，默认是输出0和1的。
[cpp] view plain copy cout.setf(ios_base::boolalpha); cout << true << endl; 2.每个表达式都是值，例如 if(x = 100),相当于x = 100;if(x); 不过我强烈要求不要这么写，容易看错，或者你觉得自己牛逼，但是看你的代码的人未必牛逼。最后还得加大自己的工作量，成为傻逼
3.这应该是冷知识，在比较旧的C++版本，for循环中的声明（就是下面的int i = 0），是不合法的， [cpp] view plain copy for (int i = 0; i < 5; i++) { } for循环中只能使用表达式，而声明不能算是表达式。 后来的一些版本，增加了一个声明表达式，让下面的for循环方式出现。但是这是一个兼容操作， 实际上，还是把i的声明提前的。 cout << i << endl;这个语句在for循环后面是合法的， 再后来，i就真的只能在for循环里面使用了。这不知道多少版本的事了。 跟着再写多一些代码：
[cpp] view plain copy int i = 0; while (i++ < 10) { cout << i << endl; } int y = (4 + i++) + (6 + i++);// 虽然i是for里面的局部变量了，在外面不能用了，但是在vs的调试工具，鼠标指向的内存居然还是显示i的内容还存在，
然后再看外面面的i，发现当前内存里面有两个i。不知道这算不算bug呢。不过并不影响使用。
4.i++和++i是不同的，不过我建议还是把这个东西独立一行。 [cpp] view plain copy int i = 0; while (i++ < 10) { cout << i << endl; } int y = (4 + i++) + (6 + i++);//这样是无法判断i自增是在（4+i++）完成之后就自增，还是整个表达式之后就自增。 可能不同的编译器也会有不同效果。所以不要把i++放进复杂的表达式中。
5.++i比i++效率更高。两个表达式都是i先自增，后返回的，只是i++自增前创建一个副本，然后自增，然后返回副本。
对于我们自己的类，效率差别会很明显。
6.基于范围的for循环，C++11新产品
[cpp] view plain copy int a[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; for (int &i : a) { cout << i << endl; }7.模拟eof
[cpp] view plain copy char ch; int count = 0; cin.get(ch); while (!cin.fail()) { cout << ch; ++count; cin.get(ch); } cout << endl << count << " characters read\n";
5.8 复习题
1.入口条件就是在进入循环的时候就检测，出口条件是先进入循环，再检测，至少可以执行一次循环。
for、while属于入口条件检测，do while属于出口条件检测。
2. 01234
[cpp] view plain copy int i; for (i = 0; i < 5; i++) cout << i; cout << endl; 3. 0369 12
[cpp] view plain copy int j; for (j = 0; j < 11; j += 3) cout << j; cout << endl << j << endl; 4. 6 8
[cpp] view plain copy int j = 5; while (++j < 9) { cout << j++ << endl; }
5.
k = 8
[cpp] view plain copy int k = 8; do cout << "k = " << k << endl; while (k++ < 5); 6.
[cpp] view plain copy for (int i = 1; i <= 64; i *= 2) { cout << i<<" "; } cout << endl; 7.使用{}，其实就算只有一条语句，也应该使用{}，可以是代码更加清晰，而且说不定什么时候需求就要变了，一条语句通常干不了什么的。
8.都有效。
[cpp] view plain copy int x = (1, 024);//x为20，（）内返回024，0开头是8进制，即是20. int y; y = 1, 024;//y=1，之后024.就没了
9.cin>>ch,跳过空格、换行符、制表符。cin.get(ch) 和 ch = cin.get()可以读取这些字符
5.9编程题
1.
[cpp] view plain copy int m = 0; int n = 0; cin >> m; cin >> n; if (m > n) { int t = m; m = n; n = t; } int total = 0; for (int i = m; i <= n; i++) { total += i; } cout << total <<endl; 2.
5.4程序清单
[cpp] view plain copy const int ArSize = 16; long long factorials[ArSize]; factorials[1] = factorials[0] = 1LL; for (int i = 2; i < ArSize; i++) { factorials[i] = i * factorials[i-1]; } for (int i = 0; i < ArSize; i++) { cout << i << " = " << factorials[i] << endl; } 修改后：
[cpp] view plain copy const int ArSize = 101; array<long double, ArSize> factorials; factorials[1] = factorials[0] = 1; for (int i = 2; i < ArSize; i++) { factorials[i] = i * factorials[i-1]; } for (int i = 0; i < ArSize; i++) { cout << i << " = " << factorials[i] << endl; } 结果：
0 = 1
1 = 1
2 = 2
3 = 6
4 = 24
5 = 120
6 = 720
7 = 5040
8 = 40320
9 = 362880
10 = 3.6288e+06
11 = 3.99168e+07
12 = 4.79002e+08
13 = 6.22702e+09
14 = 8.71783e+10
15 = 1.30767e+12
。。。好长
3. [cpp] view plain copy cout << "Please enter:" << endl; int i = -1; int total = 0; while (i != 0) { cin >> i; total += i; cout << "current sum: "<< total << endl; } 4.
[cpp] view plain copy const double base = 100; const double interestA = 0.1; const double interestB = 0.05; double moneyA = base; double moneyB = base; int year = 0; while (moneyA >= moneyB) { ++year; moneyA += (base * interestA); moneyB += (moneyB * interestB); } cout << "Year:" << year << " A:" << moneyA << " B:" << moneyB << endl; 结果：
[cpp] view plain copy <span style="font-family: Arial, Helvetica, sans-serif;">Year:27 A:370 B:373.346</span>
5.
[cpp] view plain copy string month[12] = { "January","February","March","April", "May","June","July","August", "September","October","November","December"}; int total = 0; int thisYearData[12]; for (int i = 0; i < 12; ++i) { cout << "Please enter " << month[i] <<"'data:" ; cin >> thisYearData[i]; total += thisYearData[i]; } cout << "this year' data: "<< total <<endl; 6. [cpp] view plain copy string month[12] = { "January","February","March","April", "May","June","July","August", "September","October","November","December"}; int total = 0; int yearData[3][12]; int yearTotal[3]; for (int j = 0; j < 3; ++j) { for (int i = 0; i < 12; ++i) { cout << "Please enter the " << j + 1 << " year " << month[i] <<"'data:" ; cin >> yearData[j][i]; total += yearData[j][i]; yearTotal[j] += yearData[j][i]; } } for (int i = 0; i < 3; ++i) { cout << "year:"<< i + 1 << " data:"<< yearTotal[i] << endl; } cout << "all year' data: "<< total <<endl; 7.
[cpp] view plain copy struct SCar { string manufacturer; int year; }; int num = 0; cout << "How many cars do you wish to catalog?"; cin >> num; cin.get(); SCar* carArr = new SCar[num]; for (int i = 0; i < num; ++i ) { cout<< "Car #" << i + 1 << ":"<<endl; cout<< "Please enter the make:"; getline(cin, carArr[i].manufacturer); cout << "Please enter the year made:"; cin >> carArr[i].year; cin.get(); } cout << "Here is your collection:" << endl; for (int i = 0 ; i < num; ++i) { cout << carArr[i].year << " " << carArr[i].manufacturer << endl; }
8.
[cpp] view plain copy char s[20]; int count = 0; cout << "Enter words (to stop, type the word done):" <<endl; while (true) { cin >> s; if (0 == strcmp(s, "done")) { break; }else{ ++count; } } cout << "You entered a total of " << count << " words" << endl;
9.
[cpp] view plain copy string s; int count = 0; cout << "Enter words (to stop, type the word done):" <<endl; while (true) { cin >> s; if (s == "done") { break; }else{ ++count; } } cout << "You entered a total of " << count << " words" << endl; 10.
[cpp] view plain copy cout << "Enter number of rows: "; int n = 0; cin >> n; for (int i = 0; i < n; ++i) { for (int j = 0; j < n ; ++j) { if (j < n - i - 1) { cout << "." ; }else{ cout << "*"; } } cout << endl; }
