C++Primer第五版 5.3.2节练习

练习5.9：编写一段程序，使用一系列if语句统计从cin读入的文本中有多少个元音字母。

练习5.10：我们之前实现的统计元音字母的程序存在一个问题：如果元音字母以大写字母形式出现，不会被统计在内。编写一段程序，既统计元音字母的小写形式，也统计大写形式，也就是说，新程序遇到‘a’和‘A’都应该递增aCnt的值，以此类推。

练习5.11：修改统计元音字母的程序，使其也能统计空格，制表符和换行符的数量。

练习5.12：修改统计元音字母的程序，使其能统计以下含有两个字符的字符序列的数量：ff，fl和fi。
答：练习5.9-5.12见云盘程序。

练习5.13：下面显示的每个程序都含有一个常见的编程错误，指出错误在哪里，然后修改它们。

（a）. unsigned aCnt = 0, eCnt = 0, iouCnt = 0;      char ch = next_text();      switch (ch) {      case ‘a’ : aCnt++;//缺少break       //break;case ‘e’ : eCnt++;//缺少break      //break;default: iouCnt++;//缺少break//break;}(b). unsigned index = some_value();    Switch(index) {case 1:        //int ix = get_value(); // 错误：控制流绕过一个显式初始化的变量        //ivec[ ix ] = index;  // 错误：控制流绕过一个显式初始化的变量        break;//break; default:        ix = ivec.size() – 1;    ivec [ ix ] = index;}(c).unsigned evenCnt = 0, oddCnt = 0; int digit = get_num() % 10;switch (digit){ Case 1,3,5,7,9://写法错误 case 1: case 3: case 5: case 7: case 9:  oddCnt++;case 2,4,6,8,10://case 2: case 4: case 6: case 8: case 10:  evenCnt++; break;}(d). unsigned ival = 512, jval = 1024, kval = 4096;unsigned bufsize;unsigned swt = get_bufCnt();switch(swt){case ival://错误：case标签必须是整型常量表达式。   bufsize = ival * sizeof(int);   break;case jval: //错误：case标签必须是整型常量表达式。      bufsize = javl * sizeof(int);case kval: //错误：case标签必须是整型常量表达式。      bufsize = kval * sizeof(int);      break; } 

练习5.9

#include <iostream>using namespace std;int main(){    unsigned aCnt = 0, eCnt = 0, iCnt = 0, oCnt = 0, uCnt = 0, totalCnt = 0;    char ch;    while (cin >> ch)    {        if (ch == 'a')            ++aCnt;        if (ch == 'e')            ++eCnt;        if (ch == 'i')            ++iCnt;        if (ch == 'o')            ++oCnt;        if (ch == 'u')            ++uCnt;        totalCnt = aCnt + eCnt + iCnt + oCnt + uCnt ;       }     cout << "a:" << aCnt << endl;    cout << "e:" << eCnt << endl;    cout << "i:" << iCnt << endl;    cout << "o:" << oCnt << endl;    cout << "u:" << uCnt << endl;    cout << "total:" << totalCnt << endl;     return 0;} 

练习5.10

#include <iostream>using namespace std;int main(){    unsigned aCnt =0, eCnt = 0, iCnt = 0, oCnt = 0, uCnt = 0, other = 0, vowelCnt = 0,total = 0;    char ch;    while (cin >> ch)    {        switch (ch)        {            case 'a':            case 'A':                 ++aCnt;                break;             case 'e':            case 'E':                 ++eCnt;                break;            case 'i':            case 'I':                 ++iCnt;                break;            case 'o':            case 'O':                 ++oCnt;                break;            case 'u':            case 'U':                 ++uCnt;                break;            default:                ++other;                break;           }    }        vowelCnt = aCnt + eCnt + iCnt + oCnt + uCnt;        total = vowelCnt + other;           cout << "a:" << aCnt << endl;        cout << "e:" << eCnt << endl;        cout << "i:" << iCnt << endl;        cout << "o:" << oCnt << endl;        cout << "other:" << other << endl;        cout << "vowelCnt:" << vowelCnt << endl;        cout << "total:" << total << endl;    return 0;} 

练习5.11

#include <iostream>#include <vector>#include <fstream>using namespace std;int main(){    unsigned aCnt =0, eCnt = 0, iCnt = 0, oCnt = 0, uCnt = 0, other = 0, vowelCnt = 0,total = 0, space = 0, tableSign = 0, Enter = 0;    vector<char> charVector;    char ch;    //while (cin >> ch && ch != '#')     //输入流会掠过，空格，制表符，以及回车      ifstream in("练习5-11.txt");       //这边参考网上的例子，定义一个文件流，在文件同目录下，相应建一个new.txt文件，用于读取文件里的东西      if (!in)     {        cerr << "oh , shit!" << endl;        return -1;      }     while(in.get(ch))     {        cout << ch ;        charVector.push_back(ch);     }     cout << endl;//以上打印文件里面的字符     for ( auto i = 0; i != charVector.size(); ++i)    {        switch (charVector[i])        {            case 'a':            case 'A':                 ++aCnt;                break;             case 'e':            case 'E':                 ++eCnt;                break;            case 'i':            case 'I':                 ++iCnt;                break;            case 'o':            case 'O':                 ++oCnt;                break;            case 'u':            case 'U':                 ++uCnt;                break;            case ' ':                ++space;                break;            case '\t':                ++tableSign;                break;            case '\n':                ++Enter;                break;             default:                ++other;                break;           }    }        vowelCnt = aCnt + eCnt + iCnt + oCnt + uCnt;        total = vowelCnt + other;           cout << "a:" << aCnt << endl;        cout << "e:" << eCnt << endl;        cout << "i:" << iCnt << endl;        cout << "o:" << oCnt << endl;        cout << "other:" << other << endl;        cout << "vowelCnt:" << vowelCnt << endl;        cout << "space:" << space << endl;        cout << "tableSign:" << tableSign << endl;        cout << "Enter:"  << Enter << endl;        cout << "total:" << total << endl;    return 0;} 练习5-11.txta b c d e f g h i j k l m n o p q

练习5.12

#include <iostream>#include <vector>#include <fstream>using namespace std;int main(){    unsigned aCnt =0, eCnt = 0, iCnt = 0, oCnt = 0, uCnt = 0, other = 0, vowelCnt = 0,total = 0, space = 0, tableSign = 0, Enter = 0, ffCnt = 0, flCnt = 0, fiCnt = 0;    vector<char> charVector;    char ch;    //while (cin >> ch && ch != '#') 输入流会掠过，空格，制表符，以及回车 //这边参考网上的例子，定义一个文件流，在文件同目录下，相应建一个new.txt文件，用于读取文件里的东西      if (!in)     {        cerr << "oh , shit!" << endl;        return -1;      }     while(in.get(ch))     {        cout << ch ;        charVector.push_back(ch);     }     cout << endl;//以上打印文件里面的字符     for ( auto i = 0; i != charVector.size(); ++i)    {        switch (charVector[i])        {            case 'a':            case 'A':                 ++aCnt;                break;             case 'e':            case 'E':                 ++eCnt;                break;            case 'i':            case 'I':                 ++iCnt;                break;            case 'o':            case 'O':                 ++oCnt;                break;            case 'u':            case 'U':                 ++uCnt;                break;            case ' ':                ++space;                break;            case '\t':                ++tableSign;                break;            case '\n':                ++Enter;                break;             case 'f':                if (charVector[i+1] == 'f')                 //前一个字符为f，紧接着为ff情况                     ++ffCnt;                else if (charVector[i+1] == 'l')                    ++flCnt;                    else if (charVector[i+1] == 'i')                        ++fiCnt;                       //else ;//执行一个空语句，代表上述三种情况之外的，执行一个空语句，无任何结果                 break;            default:                ++other;                break;           }    }        vowelCnt = aCnt + eCnt + iCnt + oCnt + uCnt;        total = vowelCnt + other;           cout << "a:" << aCnt << endl;        cout << "e:" << eCnt << endl;        cout << "i:" << iCnt << endl;        cout << "o:" << oCnt << endl;        cout << "other:" << other << endl;        cout << "vowelCnt:" << vowelCnt << endl;        cout << "space:" << space << endl;        cout << "tableSign:" << tableSign << endl;        cout << "Enter:"  << Enter << endl;        cout << "ffCnt:" << ffCnt << endl;        cout << "flCnt:" << flCnt << endl;        cout << "fiCnt:" << fiCnt << endl;         cout << "total:" << total << endl;    return 0;}