1 3.1
2
3 #include <iostream>
4 using std::cin;
5 using std::cout;
6 using std::endl;
7 int main()
8 {
9 int base,exponent;
10 long result=1;
11 cout<<"Enter base and exponent:"<<endl;
12 cin>>base>>exponent;
13 if(exponent<0)
14 {
15 cout<<"Exponent can‘t be smaller than 0"<<endl;
16 return -1;
17 }
18 else
19 {
20 for(int cnt=1;cnt<=exponent;++cnt)
21 {
22 result*=base;
23 }
24 }
25 cout<<base<<" raised to the power of "<<exponent<<":"<<result<<endl;
26 //cout << "Hello world!" << endl;
27 return 0;
28 }
29 3.5
30 //读入一行
31 #include<iostream>
32 using namespace std;
33 int main()
34 {
35 string word;
36 while(getline(cin,word))
37 {
38 cout<<word<<endl;
39 }
40 return 0;
41 }
42 //读入单词
43 #include<iostream>
44 using namespace std;
45 int main()
46 {
47 string word;
48 while(cin>>word)
49 {
50 cout<<word<<endl;
51 }
52 return 0;
53 }
54 3.8
55 #include<iostream>
56 using namespace std;
57 int main()
58 {
59 string result_str,str;
60 cin>>result_str;
61 while(cin>>str)
62 result_str=result_str+" "+str;
63 cout<<result_str<<endl;
64 return 0;
65 }
66 3.10
67 #include<iostream>
68 using namespace std;
69 int main()
70 {
71 bool has_punct=false;
72 string s,result_str;
73 cout<<"Enter a String:"<<endl;
74 getline(cin,s);
75 for(string::size_type index=0;index!=s.size();++index)
76 {
77 if(ispunct(s[index]))
78 {
79 has_punct=true;
80 }
81 else
82 {
83 result_str+=s[index];
84 }
85 }
86 if(has_punct)
87 cout<<"Result:"<<result_str<<endl;
88 else
89 {
90 cout<<"No punctuation character in the string"<<endl;
91 return -1;
92 }
93 return 0;
94 }
95 3.13
96 #include<iostream>
97 #include<vector>
98 using namespace std;
99 int main()
100 {
101 vector<int> ivec;
102 vector<int> sum;
103 int ival;
104 cout << "Enter numbers(Ctrl+Z to end):" << endl;
105 while(cin>>ival)
106 ivec.push_back(ival);
107 if(ivec.size()==0)
108 {
109 cout<<"No elements"<<endl;
110 }
111 for (vector<int>::size_type index=0;index<ivec.size()-1;index=index+2)
112 {
113 if(ivec.size()%2!=0)
114 {
115 if(index<ivec.size()-1)
116 {
117 sum.push_back(ivec[index]+ivec[index+1]);
118 //sum.push_back(ivec[index]+ivec[ivec.size()-2-index]);
119 }
120 }
121 else
122 {
123 sum.push_back(ivec[index]+ivec[index+1]);
124 // sum.push_back(ivec[index]+ivec[ivec.size()-1-index]);
125 }
126 }
127 if(ivec.size()%2!=0)
128 {
129 cout<<"Last element is not computed:"<<endl;
130 }
131 cout << "Sum of each pair of adjacent elements in the vector:"<<endl;
132 for (vector<int>::size_type index=0;index!=sum.size();++index)
133 {
134 cout<<sum[index]<<" ";
135 }
136 cout<<endl;
137 return 0;
138 }
139 3.14
140 #include<iostream>
141 #include<vector>
142 #include<string>
143 #include<cctype>
144 using namespace std;
145 int main()
146 {
147 cout<<"Enter some words:"<<endl;
148 vector <string> istr;
149 string iword;
150 while(cin>>iword)
151 istr.push_back(iword);
152 cout<<"After transformation:"<<endl;
153 for (vector<string>::size_type index=0;index<istr.size();++index)
154 {
155 for (string::size_type index2 = 0; index2 != istr[index].size(); ++index2)
156 {
157 istr[index][index2]=toupper(istr[index][index2]);
158 }
159 cout<<istr[index]<<"\t";
160 if((index%8==0)&&(index>0))
161 {
162 cout<<endl;
163 }
164 }
165 return 0;
166 }
167
168 3.17
169 重做3.13
170 #include<iostream>
171 #include<vector>
172 using namespace std;
173 int main()
174 {
175 vector<int> ivec;
176 vector<int> sum;
177 int ival;
178 cout << "Enter numbers(Ctrl+Z to end):" << endl;
179 while(cin>>ival)
180 ivec.push_back(ival);
181 if(ivec.size()==0)
182 {
183 cout<<"No elements"<<endl;
184 }
185 for(vector<int>::iterator it=ivec.begin();it!=ivec.end()-1;it=it+2)
186 {
187 if(ivec.size()%2!=0)
188 {
189 if(it<ivec.end()-2)
190 {
191 sum.push_back((*it)+*(it+1));
192 }
193 }
194 else
195 {
196 sum.push_back((*it)+*(it+1));
197 }
198 }
199 if(ivec.size()%2!=0)
200 {
201 cout<<"Last element is not computed:"<<endl;
202 }
203 cout << "Sum of each pair of adjacent elements in the vector:"<<endl;
204 for(vector<int>::iterator it2=sum.begin();it2!=sum.end();++it2)
205 {
206 cout<<*it2<<" ";
207 }
208 cout<<endl;
209 return 0;
210 }
211 重做3.14
212 #include<iostream>
213 #include<vector>
214 #include<string>
215 #include<cctype>
216 using namespace std;
217 int main()
218 {
219 cout<<"Enter some words:"<<endl;
220 vector <string> istr;
221 string iword;
222 while(cin>>iword)
223 istr.push_back(iword);
224 cout<<"After transformation:"<<endl;
225 for(vector<string>::iterator it=istr.begin();it!=istr.end();++it)
226 {
227 for(string::iterator it2=(*it).begin();it2!=(*it).end();++it2)
228 {
229 *it2=toupper(*it2);
230 }
231 cout<<*it<<"\t";
232 if((it-istr.begin())%8==0&&it>istr.begin())
233 {
234 cout<<endl;
235 }
236 }
237 return 0;
238 }
239
240 3.18
241 #include<iostream>
242 #include<vector>
243 using namespace std;
244 int main()
245 {
246 vector<int> ivec(10,42);
247 for (vector<int>::iterator it=ivec.begin();it!=ivec.end();++it)
248 {
249 *it=*it*2;
250 }
251 for (vector<int>::iterator it=ivec.begin();it!=ivec.end();++it)
252 {
253 cout<<*it<<"\t";
254 }
255 return 0;
256 }
257
258 4.15 解释指针和引用的主要区别。
259 使用引用（reference）和指针（pointer）都可间接访问另一个值，但它们之间存在两个重要区别：
260 (1)引用总是指向某个确定对象（事实上，引用就是该对象的别名），定义引用时没有进行初始化会出现编译错误；
261 (2) 赋值行为上存在差异：给引用赋值修改的是该引用所关联的对象的值，而不是使该引用与另一个对象关联。引用一经初始化，就始终指向同一个特定对象。给指针赋值修改的是指针对象本身，也就是使该指针指向另一对象，指针在不同时刻可指向不同的对象（只要保证类型匹配）。
262
263 4.25 C风格字符串比较
264 #include<iostream>
265 #include<string>
266 #include<cstring>
267 using namespace std;
268 int main()
269 {
270 const int str_size=80;
271 char *str1,*str2;
272 str1=new char[str_size];
273 str2=new char[str_size];
274 if(str1==NULL||str2==NULL)
275 {
276 cout<<"No enough Memory"<<endl;
277 return -1;
278 }
279 cout<<"Enter two strings:"<<endl;
280 cin>>str1>>str2;
281 int result;
282 result=strcmp(str1,str2);
283 if(result>0)
284 cout << "\"" << str1 << "\"" << " is bigger than "<< "\"" << str2 << "\"" << endl;
285 else if (result < 0)
286 cout << "\"" << str2 << "\"" << " is bigger than "<< "\"" << str1 << "\"" << endl;
287 else
288 cout << "They are equal" << endl;
289 delete[] str1;
290 delete[] str2;
291 return 0;
292 }
293 4.29
294 (a) 这两段程序的功能是：执行一个循环次数为1000000 的循环，在该循环的循环体中：创建一个新字符串，将一个已存在的字符串复制给新字符串，然后比较两个字符串，最后释放新字符串。
295 #include<iostream>
296 #include<string>
297 #include<cstring>
298 using namespace std;
299 int main()
300 {
301 const char *pc = "a very long literal string";
302 const size_t len = strlen(pc +1); // space to
303 for (size_t ix = 0; ix != 1000000; ++ix) {
304 char *pc2 = new char[len + 1]; // allocate the space
305 strcpy(pc2, pc); // do the copy
306 if (strcmp(pc2, pc)) // use the new string
307 ; // do nothing
308 delete [] pc2; // free the memory
309 }
310 string str("a very long literal string");
311 // performance test on string allocation and copy
312 for (int ix = 0; ix != 1000000; ++ix) {
313 string str2 = str; // do the copy, automatically allocated
314 if (str != str2) // use the new string
315 ; // do nothing
316 }
317 return 0;
318 }
319 4.30 字符串连接（Cstring style）
320 #include <cstring>
321 int main()
322 {
323 const char *cp1 = "Mary and Linda ";
324 const char *cp2 = "are firends.";
325 size_t len = strlen(cp1) + strlen(cp2);
326 char *result_str = new char[len+1];
327 strcpy(result_str, cp1);
328 strcat(result_str, cp2);
329 delete [] result_str;
330 return 0;
331 }
332 （C++ string style）
333 #include <string>
334 using namespace std;
335 int main()
336 {
337 const string str1("Mary and Linda ");
338 const string str2("are firends.");
339 string result_str;
340 result_str = str1;
341 result_str += str2;
342 return 0;
343 }
344 4.31 输入字符串到string，截断将string.c_str()copy到c风格字符串
345 #include <iostream>
346 #include <string>
347 #include <cstring>
348 using namespace std;
349 int main()
350 {
351 string in_str;// 用于读入字符串的string 对象
352 const size_t str_size = 10;
353 char result_str[str_size+1];// 读入字符串
354 cout << "Enter a string(<=" << str_size<< " characters):" << endl;
355 cin >> in_str;// 计算需复制的字符的数目
356 size_t len = strlen(in_str.c_str());
357 if (len > str_size)
358 {
359 len = str_size;
360 cout << "String is longer than " << str_size<< " characters and is stored only "
361 << str_size << " characters!" << endl;
362 }
363 // 复制len 个字符至字符数组result_str
364 strncpy(result_str, in_str.c_str(), len);
365 // 在末尾加上一个空字符（null 字符）
366 result_str[len+1] = ‘\0‘;
367 return 0;
368 }
369 4.32&4.33
370 //int数组赋值给vector<int>
371 #include <iostream>
372 #include <vector>
373 using namespace std;
374 int main()
375 {
376 const size_t arr_size = 8;
377 int int_arr[arr_size];// 输入数组元素
378 cout << "Enter " << arr_size << " numbers:" << endl;
379 for (size_t ix = 0; ix != arr_size; ++ix)
380 cin >> int_arr[ix];// 用int 型数组初始化vector 对象
381 vector<int> ivec(int_arr, int_arr + arr_size);
382 return 0;
383 }
384 //vector<int>赋值给int数组
385 #include <iostream>
386 #include <vector>
387 using namespace std;
388 int main()
389 {
390 vector<int> ivec;
391 int ival;// 输入vector 元素
392 cout << "Enter numbers: (Ctrl+Z to end)" << endl;
393 while (cin >> ival)
394 ivec.push_back(ival);// 创建数组
395 int *parr = new int[ivec.size()];// 复制元素
396 size_t ix = 0;
397 for (vector<int>::iterator iter = ivec.begin();iter != ivec.end(); ++iter, ++ix)
398 parr[ix] = *iter;// 释放数组
399 delete [] parr;
400 return 0;
401 }
402 4.34&4.35
403 #include <iostream>
404 #include <string>
405 #include <cstring>
406 #include <vector>
407 using namespace std;
408 int main()
409 {
410 vector<string> ivec;
411 string str;
412 cout<<"Enter strings:"<<endl;
413 while(cin>>str)
414 ivec.push_back(str);
415 char **s2ptr=new char*[ivec.size()];
416 size_t ix=0;
417 for (vector<string>::iterator it=ivec.begin();it!=ivec.end();++it,++ix)
418 {
419 char *strptr=new char[(*it).size()+1];
420 strcpy(strptr,(*it).c_str());
421 s2ptr[ix]=strptr;
422 // *s2ptr=strptr;
423 // s2ptr=s2ptr+1;
424 }
425 cout << "Content of character arrays:" << endl;
426 for (ix =0; ix != ivec.size(); ++ix)
427 cout << *(s2ptr+ix) << endl;
428 // 释放各个字符数组
429 for (ix =0; ix != ivec.size(); ++ix)
430 delete [] s2ptr[ix];
431 // 释放字符指针数组
432 delete [] s2ptr;
433 return 0;
434 }
435
436 8.3 流状态的查询和控制 ( 在保证程序的可靠性时经常遇到的问题 )
437
438 C和C++的标准里从来没有定义过 fflush(stdin)。也许有人会说：“可是我用 fflush(stdin) 解决了这个问题，你怎么能说是错的呢？”的确，某些编译器（如VC6）支持用 fflush(stdin) 来清空输入缓冲，但是并非所有编译器都要支持这个功能（linux 下的 gcc 就不支持），因为标准中根本没有定义 fflush(stdin)。MSDN 文档里也清楚地写着fflush on input stream is an extension to the C standard（fflush 操作输入流是对 C 标准的扩充）。当然，如果你毫不在乎程序的移植性，用 fflush(stdin) 也没什么大问题。以下是 C99 对 fflush 函数的定义：
439
440 /*
441 * 流状态的查询和控制
442 * 2010-3-26 wcdj
443 */
444 #include <iostream>
445 #include <stdexcept>
446 #include "stdio.h"
447 using namespace std;
448 void way1_cleario();
449 void way2_cleario();
450 int main()
451 {
452 int ival;
453 cout<<"Enter an interger:";
454 // read cin and test only for EOF;
455 // loop is executed even if there are other IO failures
456 while (cin>>ival, !cin.eof())
457 {
458 // input stream is corrupted; bail out
459 if (cin.bad())
460 {
461 throw runtime_error("IO stream corrupted");
462 }
463 // bad input
464 if (cin.fail())
465 {
466 cerr<<"bad data, try again/n";// warn the user
467 // reset the stream
468 //cin.clear(istream::failbit);// error, why?
469 cin.clear();// ok
470 way2_cleario();// eat excess bad stream
471 //way2_cleario();
472 continue;// get next input
473 }
474 // ok, to process ival
475 cout<<"ok, to process ival"<<endl;
476 }
477 return 0;
478 }
479 void way1_cleario()
480 {
481 int ival=0;
482 fflush(stdin); //不良代码，C++ codeblock下运行通过，下面代码输入要带空格
483 // 在C中，刷新缓冲区可以使用下面这样的代码
484 // 通过 while 循环把输入流中的余留数据“吃”掉
485 //一种移植性比较高的清空输入缓冲区办法
486 // while((ival=getchar())!=‘/n‘&&ival!=EOF);
487 // clearerr( stdin );
488 }
489 void way2_cleario()
490 {
491 cin.ignore(200,‘ ‘);// 输入的数据必须以空格分开，输入数据一定要有空格
492 }
493
494 8.4 文件读写
495
496 #include <fstream>
497 #include <iostream>
498 using namespace std;
499 const char * filename = "out.txt";
500 int main()
501 {
502 ofstream out;//写入文件处理
503 out.open("out.txt",ios_base::app);
504 if (out.is_open())
505 {
506 out << "This is a line.";
507 out << "This is another line.\n";
508 out.close();
509 out.clear();
510 }
511 char buffer0[256];
512 ifstream in("out.txt");//读取文件处理
513 if (! in.is_open())
514 {
515 cout << "Error opening file";
516 return 0;
517 }
518 while (!in.eof() )
519 {
520 in.getline (buffer0,100);
521 cout << buffer0 << endl;
522 }
523 }
524
525 8.5. 字符串流
526
527 #include <sstream>
528 #include <iostream>
529 using namespace std;
530 int main()
531 {
532 int val1=512,val2=1024;
533 ostringstream format_message;
534 format_message<<"val1:"<<val1<<"~"<<"val2:"<<val2<<"\n";
535 //format_message<<"val1:"<<val1<<"\n"<<"val2:"<<val2<<"\n";//这种输出，得到val1为0
536 istringstream input_istring(format_message.str());
537 cout <<format_message.str();
538 string dump;
539 input_istring >> dump >> val1 >> dump >> val2;
540 cout << val1 << " " << val2 << endl; // prints 512 1024
541 return 0;
542 }
543
544
时间： 2024-10-10 05:47:04