代码如下：

1. #include <iostream>
2. using namespace std;
3. int main() {
4. char ch;
5. char s_letter[26]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
6. char b_letter[26]={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
7. int num[26]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
8. for (int i = 1; i <= 10000; i++) {
9. ch = cin.get();
10. if(ch == '#')break;
11. for(int j=0;j<=25;j++)
12. {
13. if(ch==s_letter[j] || ch==b_letter[j]) num[j]++;
14. }
15. }
16. for(int i=0;i<=25;i++)
17. {
18. cout<<s_letter[i]<<"出现的个数为"<<num[i]<<endl;
19. }
20. }

(拓展)统计26个字母在一篇新闻中各自出现的频率。

代码如下：

1. #include <iostream>
2. using namespace std;
3. int main() {
4. char ch;
5. char s_letter[26]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
6. char b_letter[26]={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
7. int num[26]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
8. float f_num[26]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
9. int Sum;
10. for (int i = 1; i <= 10000; i++) {
11. ch = cin.get();
12. if(ch == '#')break;
13. for(int j=0;j<=25;j++)
14. {
15. if(ch==s_letter[j] || ch==b_letter[j]) num[j]++;
16. }
17. }
18. for(int i=0;i<=25;i++)
19. {
20. cout<<s_letter[i]<<"出现的个数为"<<num[i]<<endl;
21. }
22. for(int i=0;i<=25;i++)
23. {
24. Sum+=num[i]; //计算字母总数
25. }
26. for(int i=0;i<=25;i++)
27. {
28. f_num[i]=num[i]*(1.0)/Sum * 100; //计算字母出现的频率*100
29. }
30. for(int i=0;i<=25;i++)
31. {
32. cout<<s_letter[i]<<"出现的频率为";
33. printf("%.3f",f_num[i]);//保留三位小数
34. cout<<"%"<<endl;//输出频率为百分之几
35. }

}

(拓展)英文新闻由文件输入，统计其中a-z这26个字母各出现的次数和总字符个数。(不区分大小写)

1. #include <iostream>
2. #include <fstream>
3. #include <cassert>
4. #include <string>
5. #include<algorithm>
6. #include<iomanip>
7. using namespace std;
8. int main()
9. { char s_letter[26]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
10. char b_letter[26]={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
11. int num[26]={0};
12. float f_num[26]={0};
13. ifstream infile;
14. int Sum=0;
15. infile.open("C:\\Users\\yyz22\\Desktop\\news1.txt");//打开文件txt 根据自身需求更改绝对路径 注意是双反斜杠\\
16. char ch;
17. infile >> noskipws;//不跳过空格和换行
18. while (!infile.eof())//循环直到文本末尾结束
19. {
20. infile>>ch;
21. cout<<ch;
22. for(int j=0;j<=25;j++)
23. {
24. if(ch==s_letter[j] || ch==b_letter[j]) num[j]++;//统计字母出现个数
25. }
26. }
27. infile.close();
28. cout<<endl;
29. for(int i=0;i<=25;i++)
30. {
31. cout<<s_letter[i]<<"出现的个数为"<<num[i]<<endl;
32. Sum= Sum + num[i]; //计算字母总数
33. }
34. cout<<"总数："<<Sum<<"\n";
35. for(int i=0;i<=25;i++)
36. {
37. f_num[i]=float(num[i])/Sum; //计算字母出现的频率
38. }
39. for(int i=0;i<=25;i++)
40. {
41. cout<<s_letter[i]<<"出现的频率为";
42. cout<<fixed<<setprecision(6)<<f_num[i]*100;
43. cout<<"%"<<endl;//输出频率为百分之几
44. }
45. }

总结：for循环处理ch=cin.get(); 解决了enter结束输入流的问题。分别用if判断是什么字符或者#结束。

 --yyz 1806

2018.10.24