Vector vector container (summary of commonly used methods)

As for the learning of vector container in STL, it's better to watch the code after compiling and running, and see the execution result at the same time. I still want to say that it's better to watch other people's code 100 times, rather than write it by yourself.

Vector vector container can not only access elements randomly like array, but also insert elements in the tail at any time. It is simple and efficient, and can completely replace array.

The biggest highlight of vector is that it has the function of memory automatic management, which can dynamically adjust the memory space occupied when inserting and deleting elements.

It is worth noting that two important methods in the vector container, begin() returns the iterator of the first element position, and end() returns the iterator of the next element position of the last element.

  1 //about STL in vector It is better to read the code after compiling and running the container and see the execution result at the same time, but it's better to read other people's code a hundred times than to write it by yourself 
  2 #include <vector>//Header file
  3 #include <iostream>
  4 #include <algorithm>
  5 using namespace std;
  6 
  7 void print(vector <int> v);
  8 bool mycmpare(const int &a, const int &b){
  9     return a>b;
 10 }
 11 int main ()
 12 {
 13     //establish vector There are three common ways to store objects. The storage element type here is int´╝îIt could be double,char,long long Basic data types, even string Basic character sequence container 
 14     vector <int> v1;//Definition of the number of elements without specifying a container a vector container for storing integers
 15     cout<<"v1: "<<endl; 
 16     print(v1);
 17     /*Operation results
 18         v1: 
 19     Size: 0
 20     */ 
 21     
 22     vector <int> v2(5);//Defines the number of elements in the specified container. A vector container with a size of 10 is used to store integers. It is initialized to 0 by default
 23     cout<<"v2: "<<endl;
 24     print(v2);
 25     /*Operation results
 26     v2: 
 27     Size: 5
 28     0 0 0 0 0
 29     */
 30     
 31     vector <int> v3(5,1);//You can also specify an initial value, which is 1 here
 32     cout<<"v3: "<<endl;
 33     print(v3); 
 34     /*Operation results
 35     v3: 
 36     Size: 5
 37     1 1 1 1 1
 38     */
 39     
 40     //In addition, it doesn't matter whether you specify the size in advance. If you specify the size, you can use it at any time push_back()Yes vector Container tail expansion
 41     v1.push_back(1);//Emptiness oriented vector Container tail expansion, additional element is 1
 42     cout<<"v1: "<<endl; 
 43     print(v1); 
 44     v3.push_back(2);//To the vector Container tail expansion, additional element is 2
 45     cout<<"v3: "<<endl;
 46     print(v3);
 47     /*Operation results
 48     v1: 
 49     Size: 1
 50     1
 51     
 52     v3: 
 53     Size: 6
 54     1 1 1 1 1 2
 55     */
 56     
 57     //Insert element use insert()Method, requiring the insertion position to be the position of the iterator, not the subscript of the element
 58     v3.insert(v3.begin(),3);//Insert 3 at the front
 59     cout<<"v3: "<<endl;
 60     print(v3);
 61     
 62     v3.insert(v3.end(),3);//Add 3 at the end, which is equivalent to push_back()
 63     cout<<"v3: "<<endl;
 64     print(v3);
 65     /*Operation results
 66     v3: 
 67     Size: 7
 68     3 1 1 1 1 1 2
 69     
 70     v3: 
 71     Size: 8
 72     3 1 1 1 1 1 2 3
 73     */
 74      
 75     int i;
 76     for(i=0;i < v3.size();i++){//Only assigned to expanded position 
 77         v3[i]=i;
 78     }
 79     //Use when you want to delete an element or all elements in an interval erase()method
 80     v3.erase(v3.begin()+2);//Delete the second element, counting from 0
 81     cout<<"v3: "<<endl;
 82     print(v3); 
 83     /*Operation results
 84     v3: 
 85     Size: 7
 86     0 1 3 4 5 6 7
 87     */
 88     v3.erase(v3.begin()+1,v3.begin()+3);//Delete all elements in the first to third element interval
 89     cout<<"v3: "<<endl;
 90     print(v3);
 91     /*Operation results
 92     v3: 
 93     Size: 5
 94     0 4 5 6 7
 95     */
 96     //It can be seen from the results, erase()The same method insert()Method, the position of the operation is only the position of the iterator, not the subscript of the element
 97     
 98     //To empty vector(),use clear()Method delete once vector All elements in
 99     cout<<"v2: "<<endl;
100     print(v2);
101     /*Operation results
102     v2: 
103     Size: 5
104     0 0 0 0 0
105     */
106     v2.clear();
107     if(v2.empty()) cout<<"v2 After use clear()Empty after method\n"; 
108     print(v2);
109     /*Operation results
110     v2 Empty after using the clear() method
111     Size: 0
112     */
113     
114     //To reverse an iterator interval element in a vector, use the reverse()Reverse permutation algorithm,Need to add algorithm Header file 
115     cout<<"v3 Before reverse:"<<endl;
116     print(v3);
117     reverse(v3.begin(),v3.end());//Reverse all 
118     cout<<"v3 After reverse arrangement:"<<endl;
119     print(v3); 
120     /*Operation results
121     v3 Before reverse:
122     Size: 5
123     0 4 5 6 7
124     
125     v3 After reverse arrangement:
126     Size: 5
127     7 6 5 4 0
128     */
129     
130     //To sort an iterator interval element in a vector, use the sort()algorithm
131     cout<<"v3 Before ascending:"<<endl;
132     print(v3); 
133     sort(v3.begin(),v3.end());//Default ascending
134     cout<<"v3 After ascending:"<<endl;
135     print(v3);
136     /*Operation results
137     v3 Before ascending:
138     Size: 5
139     7 6 5 4 0
140     
141     v3 After ascending:
142     Size: 5
143     0 4 5 6 7
144     */
145     
146     //Custom sort comparison function, descending here
147     cout<<"v3 Before descending:"<<endl;
148     print(v3);
149     sort(v3.begin(),v3.end(),mycmpare); 
150     cout<<"v3 After descending:"<<endl;
151     print(v3);
152     /*Operation results
153     v3 Before descending:
154     Size: 5
155     0 4 5 6 7
156     
157     v3 After descending:
158     Size: 5
159     7 6 5 4 0
160     */
161 } 
162 
163 void print(vector <int> v) 
164 {
165     //cout<<"Subscript access:"<<endl;
166     cout<<"The size is:"<<v.size()<<endl; 
167     int i;
168     for(i=0;i< v.size();i++){
169         cout<<v[i]<<' ';
170     }
171     cout<<endl<<endl;
172     
173     /*cout<<"Access with iterator: "< endl;
174     //Define iterator variable it, with the type consistent with the container element type 
175     vector<int>::iterator it; 
176     for(it=v.begin(); it != v.end(); it++){
177         cout<<*it<<' ';
178     }
179     cout<<endl<<endl;*/
180 }

Posted on Wed, 13 May 2020 12:04:20 -0400 by Beans