1 //4.10  设计一个程序，输入实型变量x和y，若x>y，则输出 x-y;若x<y,则输出 y-x。
  2 #include <iostream.h>
  3 #include <stdio.h>
  4 void main()
  5 {
  6     int x,y;
  7     printf("请输入两个数，中间用空格隔开:\n");
  8     cin>>x>>y;
  9     if(x>y)
 10         cout<<x-y<<endl;
 11     else
 12         cout<<y-x<<endl;
 13 }
 14 // 4.11
 15 #include <iostream.h>
 16 #include <stdio.h>
 17 #include <math.h>
 18 void main()
 19 {
 20     int x,i,j,b,c,d,e;
 21     int a=0;
 22     printf("请输入一个数:\n");
 23     cin>>x;
 24     b=x;
 25     while(b>0)
 26     {
 27         i=b%10;
 28         b=b/10;
 29         a++;
 30     }
 31     cout<<"输入数为"<<a<<"位数"<<endl;
 32     printf("输入数的每一位数为：\n");
 33     c=x;
 34     while(c>0&&a>0)
 35     {
 36         d=c/pow(10,(a-1));
 37         c-=d*pow(10,(a-1));
 38         cout<<d<<endl;
 39         a--;
 40     }
 41     cout<<"与输入数逆序为："<<endl;
 42     while(x>0)
 43     {
 44         j=x%10;
 45         x/=10;
 46         cout<<j;
 47     }
 48     cout<<endl;
 49 }
 50 
 51 // 4.12
 52 #include <iostream.h>
 53 void main()
 54 {
 55     float i,j,a,b;
 56     cout<<"请输入若干个数，中间用空格隔开，并以“.”号结束"<<endl;
 57     cin>>i>>j;
 58     while(i>0&&j>0){
 59         if (i>j)
 60         {
 61             cin>>j;
 62             a=i;
 63         }
 64         else
 65         {
 66             cin>>i;
 67             b=j;
 68         }
 69     }
 70     if(a>b)
 71         cout<<a<<endl;
 72     else
 73         cout<<b<<endl;
 74 }
 75 
 76 // 4.13
 77 #include <iostream.h>
 78 void main()
 79 {
 80     float a,b,c;
 81     cout<<"请输入若3个数，中间用空格隔开"<<endl;
 82     cin>>a>>b>>c;
 83     if(a+b>c&&a+c>b&&b+c>a)
 84         cout<<"这三个数能构成三角形的三边"<<endl;
 85     else
 86         cout<<"这三个数不能构成三角形的三边"<<endl;
 87 }
 88 
 89 // 4.14
 90 #include <iostream.h>
 91 void main()
 92 {
 93     int a,b,c;
 94     cout<<"请输入若3个数，中间用空格隔开"<<endl;
 95     cin>>a>>b>>c;
 96     if(a+b>c&&a+c>b&&b+c>a)
 97         cout<<"这三个数能构成三角形的三边"<<endl;
 98     else
 99         cout<<"这三个数不能构成三角形的三边"<<endl;
100 }
101 
102 // 4.15
103 #include <iostream.h>
104 void main()
105 {
106     int i,j;
107     int a=1;
108     cout<<"二进制"<<'\t'<<"十进制"<<'\t'<<"八进制"<<'\t'<<"十六进制"<<endl;
109     for(;a<=156;a++)
110     {
111         i=a;
112         while (i>0)
113         {
114             j=i%2;i=i/2;
115             cout<<j;
116         }
117         cout<<'\t'<<dec<<a<<'\t'<<oct<<a<<'\t'<<hex<<a<<endl;
118     }
119     
120 }
121 // 4.16
122 #include <iostream.h>
123 void main()
124 {
125     int a,b,c,d;
126     int max1,max2,min1,min2;
127     cout<<"请输入四个数"<<endl;
128     cin>>a>>b>>c>>d;
129     if(a>b)
130     {
131         max1=a;
132         min1=b;
133     }
134     else
135     {
136         max1=b;
137         min1=a;
138     }
139     if(c>d)
140     {
141         max2=c;
142         min2=d;
143     }
144     else
145     {
146         max2=d;
147         min2=c;
148     }
149     cout<<"这四个数由大到小的排列顺序为："<<endl;
150     if(max1>max2)
151     {
152         cout<<max1<<" ";
153         if(min1>min2)
154         {
155             if(max2>min1)
156                 cout<<max2<<" "<<min1<<" "<<min2<<endl;
157             else
158                 if(max2>min2)
159                     cout<<min1<<" "<<max2<<" "<<min2<<endl;
160                 else
161                     cout<<min1<<" "<<min2<<" "<<max2<<endl;
162         }
163         else
164         {
165             if(max2>min2)
166                 cout<<max2<<" "<<min2<<" "<<min1<<endl;
167             else
168                 if(max2>min1)
169                     cout<<min2<<" "<<max2<<" "<<min1<<endl;
170                 else
171                     cout<<min2<<" "<<min1<<" "<<max2<<endl;
172         }
173     }
174     else
175     {
176         cout<<max2<<" ";
177         if(min1>min2)
178         {
179             if(max1>min1)
180                 cout<<max1<<" "<<min1<<" "<<min2<<endl;
181             else
182                 if(max1>min2)
183                     cout<<min1<<" "<<max1<<" "<<min2<<endl;
184                 else
185                     cout<<min1<<" "<<min2<<" "<<max1<<endl;
186         }
187         else
188         {
189             if(max1>min2)
190                 cout<<max1<<" "<<min2<<" "<<min1<<endl;
191             else
192                 if(max1>min1)
193                     cout<<min2<<" "<<max1<<" "<<min1<<endl;
194                 else
195                     cout<<min2<<" "<<min1<<" "<<max1<<endl;
196         }
197     }
198     
199 }
200 // 4.17
201 #include <iostream.h>
202 void main()
203 {
204     cout<<"请按照下面方程的格式，分别输入六个参数，中间用空格隔开"<<endl;
205     cout<<"a1x+b1y=c1"<<endl<<"a2x+b2y=c2"<<endl;
206     float a1,a2,b1,b2,c1,c2,x,y;
207     cout<<"请按顺序输入 a1,b1,c1,a2,b2,c2"<<endl;
208     cin>>a1>>b1>>c1>>a2>>b2>>c2;
209     x=(b2*c1-b1*c2)/(a1*b2-a2*b1);
210     y=(a2*c1-a1*c2)/(a2*b1-a1*b2);
211     cout<<"x="<<x<<endl;
212     cout<<"y="<<y<<endl;
213 }
214 // 4.18
215 #include <iostream.h>
216 void main()
217 {
218     cout<<"请输入一个百分制的成绩"<<endl;
219     int a;
220     cin>>a;
221     if(a<0||a>100)
222     {
223         cout<<"你输入一个错误的数字，请重新输入"<<endl;
224     }
225     switch(a/10)
226     {
227     case 9:
228         cout<<"A"<<endl;
229         break;
230     case 8:
231         cout<<"B"<<endl;
232         break;
233     case 7:
234         cout<<"C"<<endl;
235         break;
236     case 6:
237         cout<<"D"<<endl;
238         break;
239     case 5:
240     case 4:
241     case 3:
242     case 2:
243     case 1:
244     case 0:
245         cout<<"E"<<endl;
246         break;
247     }
248 }
249 
250 //  4.19
251 #include <iostream.h>
252 void main()
253 {
254     cout<<"请输入一个正整数"<<endl;
255     int a,b;
256     int c=0;
257     cin>>a;
258     int i=2;
259     cout<<"该正数的因子为："<<endl;
260     for(;i<=a;i++)
261     {
262         b=c;
263         if(a%i==0)
264             c=a/i;
265         if(c!=b)
266             cout<<c<<endl;
267     }
268     
269 }
270 //  4.20
271 #include <iostream.h>
272 void main()
273 {
274     cout<<"请输入一个正整数"<<endl;
275     int a,i;
276     int sum=0;
277     cin>>a;
278     for (;a>0;)
279     {
280         i=a%10;
281         sum+=i;
282         a/=10;
283     }
284     cout<<"这个正整数的各位数字的和为："<<sum<<endl;
285 }
286 
287 //  4.21
288 #include <iostream.h>
289 #include <stdio.h>
290 void main()
291 {
292     int a=2;
293     int b=1;
294     float sum=0;
295     for(int i=1;i<=20;i++){
296         sum+=(float)(a)/b;
297         int c;
298         c=a+b;
299         b=a;
300         a=c;
301     }
302     cout<<"数列的和为："<<sum<<endl;
303 }
304 
305 //  4.22
306 #include <iostream.h>
307 void main()
308 {
309     int a,b,c,sum;
310     for(int i=100;i<1000;i++)
311     {
312         a=(i/100)%10;b=(i/10)%10;c=i%10;
313         sum=a*a*a+b*b*b+c*c*c;
314         if(sum==i)
315             cout<<"水仙花数为:"<<sum<<endl;
316     }
317 }
318 
319 //  4.23
320 #include <iostream.h>
321 void main()
322 {
323     int b;
324     int a=1;
325     cout<<"1000以内的完数为："<<endl;
326     while(a<1000)
327     {
328         int sum=0;
329         for(int i=2;i<=a;i++)
330         {
331             int c=0;
332             b=c;
333             if(a%i==0)
334                 c=a/i;
335             if(c!=b)
336                 sum+=c;
337         }
338         if(sum==a)
339             cout<<sum<<endl;
340         a++;
341     }
342 }
343 
344 //  4.24
345 #include <iostream.h>
346 void main()
347 {
348     float d;
349     float a=0;
350     float b=1;
351     float c=2;
352     cout<<a<<endl<<b<<endl<<c<<endl;
353     for(int n=3;n<=19;n++)
354     {
355         d=b*c+a;
356         a=b;
357         b=c;
358         c=d;
359         cout<<c<<endl;
360     }
361 }
362 
363 //  4.25
364 #include <iostream.h>
365 void main()
366 {
367     float c,F;
368     cout<<"请输入一个华氏度"<<endl;
369     cin>>F;
370     c=(F-32)*5/9;
371     cout<<"这个华氏度所对应的摄氏度为："<<c<<endl;
372 }
373 4.26
374 //  4.26
375 #include <iostream.h>
376 void main()
377 {
378     int i;
379     int a=1;
380     int sum=0;
381     cout<<"请输入若干个整数，中间用空格隔开"<<endl;
382     cin>>i;
383     while(i>=0)
384     {
385         sum+=i;
386         cin>>i;
387         cout<<"sum="<<sum<<' '<<a<<endl;
388         a++;
389     }
390 }
391 // 4.27
392 #include <iostream.h>
393 void main()
394 { 
395     cout<<" C++程序设计   p103 4.27   第一个图"<<endl<<endl;
396     for(int i=1;i<=10;i++)
397     {
398         for(int j=1;j<=i;j++)
399             cout<<'*';
400         cout<<endl;
401     }
402     cout<<endl<<" C++程序设计   p103 4.27 第二个图"<<endl<<endl;
403     for (int a=1;a<=10;a++)
404     {
405         for(int b=10;b>=a;b--)
406             cout<<'*';
407         cout<<endl;
408     }
409     cout<<endl<<" C++程序设计   p103 4.27 第三个图"<<endl<<endl;
410     for (int c=1;c<=10;c++)
411     {
412         for(int d=1;(c-d)>0;d++)
413             cout<<" ";
414         for(int e=10;e>=c;e--)
415             cout<<'*';
416         cout<<endl;
417     }
418     cout<<endl<<" C++程序设计   p103 4.27 第四个图"<<endl<<endl;
419     for (int f=1;f<=10;f++)
420     {
421         for(int g=10;g>=f;g--)
422             cout<<" ";
423         for(int h=1;(f-h)>=0;h++)
424             cout<<'*';
425         cout<<endl;
426     }
427     cout<<endl<<" C++程序设计   p103 4.27 四个图并排输出"<<endl<<endl;
428     // while的用法和for差不多，最后一个就用while，做一遍
429     int x=1;
430     while(x<=10)
431     {
432         int a1=1;
433         while(a1<=x)
434         {
435             cout<<'*';
436             a1++;
437         }
438         int b1=10;
439         while(b1>=x)
440         {
441             cout<<" ";
442             b1--;
443         }
444         int b2=10;
445         while(b2>=x)
446         {
447             cout<<'*';
448             b2--;
449         }
450         int a2=1;
451         while(a2<=x)
452         {
453             cout<<" ";
454             a2++;
455         }
456         int a3=1;
457         while(a3<=x)
458         {
459             cout<<" ";
460             a3++;
461         }
462         int b3=10;
463         while(b3>=x)
464         {
465             cout<<'*';
466             b3--;
467         }
468         int b4=10;
469         while(b4>=x)
470         {
471             cout<<" ";
472             b4--;
473         }
474         int a4=1;
475         while(a4<=x)
476         {
477             cout<<'*';
478             a4++;
479         }
480         x++;
481         cout<<endl;
482     }
483     cout<<endl;
484 }
485 // 4.28
486 #include <iostream.h>
487 int main()
488 { 
489     char A,B,C;
490     int count=1;
491     for(A='X';A<='Z';A++)
492         for(B='X';B<='Z';B++)
493             for(C='X';C<='Z';C++)
494                 if((A!=B && B!=C && C!=A) && (C!='Y') && (A!='X'))
495                 {
496                     cout<<"第"<<count<<"种名单:"<<endl;
497                     cout<<"A-"<<A<<endl;
498                     cout<<"B-"<<B<<endl;
499                     cout<<"C-"<<C<<endl;
500                     count++;
501                 }
502 }