如果需要一个没有重复元素并且已经排过序的序列
得到结果可以是一个集合set
对两个容器的性能进行比较将会有帮助
//: C07:ListVsSet.cpp
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
// Comparing list and set performance.
#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <iterator>
#include <list>
#include <set>
#include "PrintContainer.h"
using namespace std;
class Obj {
int a[20]; // To take up extra space
int val;
public:
Obj() : val(rand() % 500) {}
friend bool
operator<(const Obj& a, const Obj& b) {
return a.val < b.val;
}
friend bool
operator==(const Obj& a, const Obj& b) {
return a.val == b.val;
}
friend ostream&
operator<<(ostream& os, const Obj& a) {
return os << a.val;
}
};
struct ObjGen {
Obj operator()() { return Obj(); }
};
int main() {
const int SZ = 5000;
srand(time(0));
list<Obj> lo;
clock_t ticks = clock();
generate_n(back_inserter(lo), SZ, ObjGen());
lo.sort();
lo.unique();
cout << "list:" << clock() - ticks << endl;
set<Obj> so;
ticks = clock();
generate_n(inserter(so, so.begin()),
SZ, ObjGen());
cout << "set:" << clock() - ticks << endl;
print(lo);
print(so);
getchar();
} ///:~输出
list:270
set:39
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
输出到499
另一个从0输出到499
当运行程序 发现set比list快得多
毕竟，set的主要工作就是在排过序的序列只保存独一无二的元素
使用了头文件PrintContainer.h,其中包含一个函数模板
函数模板用于将任何序列容器打印到一个输出流
//: C07:PrintContainer.h
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
// Prints a sequence container
#ifndef PRINT_CONTAINER_H
#define PRINT_CONTAINER_H
#include "../C06/PrintSequence.h"
template<class Cont>
void print(Cont& c, const char* nm = "",
const char* sep = "\n",
std::ostream& os = std::cout) {
print(c.begin(), c.end(), nm, sep, os);
}
#endif ///:~定义的模板print()调用PrintSequence.h定义的函数模板print()