我的程序运行正常，除了一个我似乎无法弄清楚的小问题。开始时，我希望用户输入一个排序方法，然后在指针数组中输入值，直到用户用^ D结束输入。用户结束输入后，我的程序根据所需的排序方法从最高到最低打印用户输入。同样，我已经完成所有工作并且排序确实发生了，但我想要做的是基于用户输入的顺序打印，如果排序方法的两个值相同。这是我的代码，如果需要进一步说明，请问。
的main.cpp
5 #include<iostream>
6 using namespace std;
7
8 #include "video.h"
9
10 #include<string>
11
12 int main()
13 {
14 const int MAX = 100; // maximum number of things stored in the array
15 Video *vids[MAX]; // Video pointer for Video objects
16 int num_vids = 0; // counter for number of videos
17
18 string title, url, comment; // for title, url, and comment respectively
19 float length; // for length
20 int rating; // for rating
21
22 string sort; // for sorting method
23
24 cout << "How would you like to sort these videos, by rating, length, or title? " << endl;
25 cin >> sort;
26 cin.ignore();
27
28 if( (sort != "length") && (sort != "rating") && (sort != "title") )
29 {
30 cerr << sort << " is not a legal sorting method, giving up." << endl;
31 return 1;
32 }
33
34 cout << "Enter a Title: " << endl;
35 while(getline(cin,title))
36 {
37 cout << "Enter the URL: " << endl;
38 getline(cin,url);
39
40 cout << "Enter a comment: " << endl;
41 getline(cin,comment);
42
43 cout << "Enter the length: " << endl;
44 cin >> length;
45
46 cout << "Enter a rating of 1-5: " << endl;
47 cin >> rating;
48 cin.ignore();
49
50 vids[num_vids] = new Video(title,url,comment,length,rating);
51 num_vids++;
52
53 cout << "Enter a Title: " << endl;
54 }
55 cout << endl;
56
57 if( (num_vids > MAX) )
58 {
59 cerr << "Too many video entries, giving up." << endl;
60 return 1;
61 }
62
63 if( (sort == "length") )
64 {
65 for(int last = num_vids-1; last > 0; last--)
66 for(int cur = 0; cur < last; cur++)
67 if( (vids[cur]->longer(vids[cur+1]) == false) )
68 swap(vids[cur], vids[cur+1]);
69 }
70
71 else if( (sort == "rating") )
72 {
73 for(int last = num_vids-1; last > 0; last--)
74 for(int cur = 0; cur < last; cur++)
75 if( (vids[cur]->largerRating(vids[cur+1]) == false) )
76 // if( (vids[cur] != vids[cur+1]) )
77 swap(vids[cur], vids[cur+1]);
78 }
79 else if( (sort == "title") )
80 {
81 for(int last = num_vids-1; last > 0; last--)
82 for(int cur = 0; cur < last; cur++)
83 if( (vids[cur]->alphabetical(vids[cur+1]) == false) )
84 swap(vids[cur], vids[cur+1]);
85 }
86
87
88 for(int i = 0; i < num_vids; i++)
89 {
90 vids[i]->print();
91 }
92 return 0;
93 }
video.cpp
5 #include<iostream>
6 using namespace std;
7
8 #include<string>
9
10 #include "video.h"
11
12 using namespace std;
13
14 Video::Video(string title, string url, string comment, float length, int rating)
15 {
16 m_title = title;
17 m_url = url;
18 m_comment = comment;
19 m_rating = rating;
20 m_length = length;
21 }
22
23 Video::~Video()
24 {
25 cout << "object is desructing" << endl;
26 }
27
28 bool Video::longer(Video *other)
29 {
30 return m_length > other->m_length;
31 if( (other->m_length > m_length) )
32 {
33 return true;
34 }else
35 {
36 return false;
37 };
38 }
39
40 bool Video::largerRating(Video *other)
41 {
42 return m_rating > other->m_rating;
43 if( (other->m_rating > m_length) )
44 {
45 return true;
46 }
47 else
48 {
49 return false;
50 };
51 }
52
53 bool Video::alphabetical(Video *other)
54 {
55 return other->m_title > m_title;
56 if( (other->m_title > m_title) )
57 {
58 return true;
59 }else
60 {
61 return false;
62 };
63 }
64
65 void Video::print()
66 {
67 cout << m_title << ", " << m_url << ", " << m_comment << ", " << m_length << ", ";
68 for(int i = 0; i < m_rating; i++)
69 {
70 cout << "*";
71 }
72 cout << endl;
73 }
74
video.h
5 #ifndef VIDEO_H
6 #define VIDEO_H
7
8 #include<iostream>
9 using namespace std;
10
11 #include<string>
12
13 class Video
14 {
15 public:
16 Video(string title, string url, string comment,float length, int rating);
17 ~Video();
18 bool longer(Video *other);
19 bool largerRating(Video *other);
20 bool alphabetical(Video *other);
21 void print();
22
23 private:
24 string m_title;
25 string m_url;
26 string m_comment;
27 float m_length;
28 int m_rating;
29 };
30
31 #endif
同样，它的大部分都在工作，但是如果所需排序方法的两个值相同，我不希望我的程序交换冒泡排序，我尝试过这样的事情：
71 else if( (sort == "rating") )
72 {
73 for(int last = num_vids-1; last > 0; last--)
74 for(int cur = 0; cur < last; cur++)
75 if( (vids[cur]->largerRating(vids[cur+1]) == false) )
76 if( (vids[cur] != vids[cur+1]) )
77 swap(vids[cur], vids[cur+1]);
78 }
但是，仍然没有运气。任何输入都会有很大的意义。
答案 0 :(得分：0)
此问题可能有两种原因：
1-您正在比较可能导致精度问题的浮点数或双精度数，因此，浮点类型之间的比较不应该像这样（例如）：
double a,b;
//some code that defines a and b
if(a == b) //this is very bad
//do something
这可能会导致精度问题，因为像float和double这样的浮动类型可能具有最不显着的位精度问题，因此比较应该是以下形式：
if(a - b <= std::numeric_limits<float>::epsilon)
//do something
阅读有关比较浮点变量的更多信息
2-您的比较比较器导致问题，例如，而不是
if(a <= b)
使用
if(a < b)
反之亦然。试试两个！
答案 1 :(得分：-1)
只需更改您的交换条件：
for(int last = num_vids-1; last > 0; last--) {
for(int cur = 0; cur < last; cur++) {
if(vids[cur+1]->largerRating(vids[cur]) ) {
swap(vids[cur], vids[cur+1]);
}
}
}
请注意，将布尔值与布尔值进行比较完全是多余的，所以不要写这样的条件：
if(condition == true) {
if(negated == false) {
你应该写
if(condition) {
if(!negated) {
毕竟这就是bool的用途。