C++ 中的无序映射向量与示例
向量：
Vector ：它与动态数组相同，能够在插入或删除元素时自动调整自身大小，其存储由容器自动处理。向量元素被放置在连续存储中，以便可以使用迭代器访问和遍历它们。
与向量一起使用的一些函数：
- 开始（） ：它 返回指向向量中第一个元素的迭代器
- end() ：它返回一个迭代器，指向向量中最后一个元素之后的理论元素
- size() ：它返回向量中的元素数。
无序地图：
Unordered_map是一个关联容器，它存储由键值和映射值组合形成的元素。键值用于唯一标识元素，映射的值是与键关联的内容。键和值都可以是预定义或用户定义的任何类型。无序映射中的元素没有按任何特定顺序排列。在内部，使用Hash Table实现无序映射。
与无序映射一起使用的一些函数：
- at()： C++ unordered_map 中的此函数返回对以元素为键 k 的值的引用。
- begin()：返回一个迭代器，指向unordered_map容器中容器的第一个元素
- end()：返回一个迭代器，指向 unordered_map 容器中容器中最后一个元素之后的位置
本文重点介绍如何在 C++ 中使用无序映射向量。在设计复杂的数据结构时，无序映射向量非常有用。
下面是使用无序映射向量的实现：
示例 1：
C++
// C++ program to illustrate the working
// of vector of unordered maps
#include
using namespace std;
// Function to print vector elements
void print(vector >& vect)
{
cout << "vector : \n";
for (int i = 0; i < (int)vect.size(); i++) {
// Each element of the vector is a unordered map
unordered_map unorderedMap = vect[i];
cout << "unordered map : ";
cout << "[ ";
// Print unordered map elements
for (auto it = unorderedMap.begin();
it != unorderedMap.end(); it++) {
cout << it->first << ':' << it->second << " ";
}
cout << "]\n";
}
}
// Driver Code
int main()
{
// Declaring a vector of unordered maps
vector > vect;
// Declaring a unordered map
unordered_map unorderedMap1;
// Hashing values
unorderedMap1[2] = 1;
unorderedMap1[4] = 7;
unorderedMap1[6] = 10;
// Push back the unordered map in the vector
vect.push_back(unorderedMap1);
// Declaring another unordered map
unordered_map unorderedMap2;
// Hashing values
unorderedMap2[14] = 11;
unorderedMap2[15] = 21;
unorderedMap2[6] = 34;
// Push back the unordered map in the vector
vect.push_back(unorderedMap2);
// Declaring another unordered map
unordered_map unorderedMap3;
// Hashing values
unorderedMap3[7] = 277;
unorderedMap3[18] = 188;
unorderedMap3[9] = 399;
// Push back the unordered map in the vector
vect.push_back(unorderedMap3);
// Declaring another unordered map
unordered_map unorderedMap4;
// Hashing values
unorderedMap4[121] = 88;
unorderedMap4[97] = 99;
unorderedMap4[197] = 199;
// Push back the unordered map in the vector
vect.push_back(unorderedMap4);
print(vect);
return 0;
} C++
// C++ program to illustrate the working
// of vector of unordered maps
#include
using namespace std;
// Function to print vector elements
void print(vector >& vect)
{
cout << "vector : \n";
for (int i = 0; i < (int)vect.size(); i++) {
// Each element of the vector is a unordered map
unordered_map unorderedMap = vect[i];
cout << "unordered map : ";
cout << "[ ";
// Print unordered map elements
for (auto it = unorderedMap.begin();
it != unorderedMap.end(); it++) {
cout << it->first << ':' << it->second << " ";
}
cout << "]\n";
}
}
// Driver Code
int main()
{
// Declaring a vector of unordered maps
vector > vect;
// Declaring a unordered map
unordered_map unorderedMap1;
// Hashing values
unorderedMap1[11] = "Geeks";
unorderedMap1[23] = "for";
unorderedMap1[32] = "Geeks";
// Push back the unordered map in the vector
vect.push_back(unorderedMap1);
// Declaring another unordered map
unordered_map unorderedMap2;
// Hashing values
unorderedMap2[12] = "Python";
unorderedMap2[32] = "Java";
unorderedMap2[73] = "C++";
// Push back the unordered map in the vector
vect.push_back(unorderedMap2);
// Declaring another unordered map
unordered_map unorderedMap3;
// Hashing values
unorderedMap3[11] = "PHP";
unorderedMap3[2] = "C#";
unorderedMap3[35] = "Assembly";
// Push back the unordered map in the vector
vect.push_back(unorderedMap3);
// Declaring another unordered map
unordered_map unorderedMap4;
// Hashing values
unorderedMap4[14] = "C";
unorderedMap4[27] = "Javascript";
unorderedMap4[54] = "Swift";
// Push back the unordered map in the vector
vect.push_back(unorderedMap4);
print(vect);
return 0;
} C++
// C++ program to illustrate the working
// of vector of unordered maps
#include
using namespace std;
// Function to print vector elements
void print(vector >& vect)
{
cout << "vector : \n";
for (int i = 0; i < (int)vect.size(); i++) {
// Each element of the vector is a unordered map
unordered_map unorderedMap = vect[i];
cout << "unordered map : ";
cout << "[ ";
// Print unordered map elements
for (auto it = unorderedMap.begin();
it != unorderedMap.end(); it++) {
cout << it->first << ':' << it->second << " ";
}
cout << "]\n";
}
}
// Driver Code
int main()
{
// Declaring a vector of unordered maps
vector > vect;
// Declaring a unordered map
unordered_map unorderedMap1;
// Hashing values
unorderedMap1[2] = 'G';
unorderedMap1[7] = 'e';
unorderedMap1[12] = 'e';
unorderedMap1[14] = 'k';
unorderedMap1[21] = 's';
// Push back the unordered map in the vector
vect.push_back(unorderedMap1);
// Declaring another unordered map
unordered_map unorderedMap2;
// Hashing values
unorderedMap2[13] = 'J';
unorderedMap2[15] = 'a';
unorderedMap2[24] = 'v';
unorderedMap2[27] = 'a';
// Push back the unordered map in the vector
vect.push_back(unorderedMap2);
// Declaring another unordered map
unordered_map unorderedMap3;
// Hashing values
unorderedMap3[33] = 'P';
unorderedMap3[37] = 'y';
unorderedMap3[41] = 't';
unorderedMap3[19] = 'h';
unorderedMap3[43] = 'o';
unorderedMap3[53] = 'o';
// Push back the unordered map in the vector
vect.push_back(unorderedMap3);
// Declaring another unordered map
unordered_map unorderedMap4;
// Hashing values
unorderedMap4[15] = 's';
unorderedMap4[53] = 'w';
unorderedMap4[16] = 'i';
unorderedMap4[23] = 'f';
unorderedMap4[27] = 't';
// Push back the unordered map in the vector
vect.push_back(unorderedMap4);
print(vect);
return 0;
} 输出
vector :
unordered map : [ 6:10 2:1 4:7 ]
unordered map : [ 6:34 14:11 15:21 ]
unordered map : [ 9:399 7:277 18:188 ]
unordered map : [ 197:199 121:88 97:99 ]示例 2：
C++
// C++ program to illustrate the working
// of vector of unordered maps
#include
using namespace std;
// Function to print vector elements
void print(vector >& vect)
{
cout << "vector : \n";
for (int i = 0; i < (int)vect.size(); i++) {
// Each element of the vector is a unordered map
unordered_map unorderedMap = vect[i];
cout << "unordered map : ";
cout << "[ ";
// Print unordered map elements
for (auto it = unorderedMap.begin();
it != unorderedMap.end(); it++) {
cout << it->first << ':' << it->second << " ";
}
cout << "]\n";
}
}
// Driver Code
int main()
{
// Declaring a vector of unordered maps
vector > vect;
// Declaring a unordered map
unordered_map unorderedMap1;
// Hashing values
unorderedMap1[11] = "Geeks";
unorderedMap1[23] = "for";
unorderedMap1[32] = "Geeks";
// Push back the unordered map in the vector
vect.push_back(unorderedMap1);
// Declaring another unordered map
unordered_map unorderedMap2;
// Hashing values
unorderedMap2[12] = "Python";
unorderedMap2[32] = "Java";
unorderedMap2[73] = "C++";
// Push back the unordered map in the vector
vect.push_back(unorderedMap2);
// Declaring another unordered map
unordered_map unorderedMap3;
// Hashing values
unorderedMap3[11] = "PHP";
unorderedMap3[2] = "C#";
unorderedMap3[35] = "Assembly";
// Push back the unordered map in the vector
vect.push_back(unorderedMap3);
// Declaring another unordered map
unordered_map unorderedMap4;
// Hashing values
unorderedMap4[14] = "C";
unorderedMap4[27] = "Javascript";
unorderedMap4[54] = "Swift";
// Push back the unordered map in the vector
vect.push_back(unorderedMap4);
print(vect);
return 0;
}
输出
vector :
unordered map : [ 32:Geeks 11:Geeks 23:for ]
unordered map : [ 73:C++ 12:Python 32:Java ]
unordered map : [ 35:Assembly 11:PHP 2:C# ]
unordered map : [ 54:Swift 14:C 27:Javascript ]示例 3：
C++
// C++ program to illustrate the working
// of vector of unordered maps
#include
using namespace std;
// Function to print vector elements
void print(vector >& vect)
{
cout << "vector : \n";
for (int i = 0; i < (int)vect.size(); i++) {
// Each element of the vector is a unordered map
unordered_map unorderedMap = vect[i];
cout << "unordered map : ";
cout << "[ ";
// Print unordered map elements
for (auto it = unorderedMap.begin();
it != unorderedMap.end(); it++) {
cout << it->first << ':' << it->second << " ";
}
cout << "]\n";
}
}
// Driver Code
int main()
{
// Declaring a vector of unordered maps
vector > vect;
// Declaring a unordered map
unordered_map unorderedMap1;
// Hashing values
unorderedMap1[2] = 'G';
unorderedMap1[7] = 'e';
unorderedMap1[12] = 'e';
unorderedMap1[14] = 'k';
unorderedMap1[21] = 's';
// Push back the unordered map in the vector
vect.push_back(unorderedMap1);
// Declaring another unordered map
unordered_map unorderedMap2;
// Hashing values
unorderedMap2[13] = 'J';
unorderedMap2[15] = 'a';
unorderedMap2[24] = 'v';
unorderedMap2[27] = 'a';
// Push back the unordered map in the vector
vect.push_back(unorderedMap2);
// Declaring another unordered map
unordered_map unorderedMap3;
// Hashing values
unorderedMap3[33] = 'P';
unorderedMap3[37] = 'y';
unorderedMap3[41] = 't';
unorderedMap3[19] = 'h';
unorderedMap3[43] = 'o';
unorderedMap3[53] = 'o';
// Push back the unordered map in the vector
vect.push_back(unorderedMap3);
// Declaring another unordered map
unordered_map unorderedMap4;
// Hashing values
unorderedMap4[15] = 's';
unorderedMap4[53] = 'w';
unorderedMap4[16] = 'i';
unorderedMap4[23] = 'f';
unorderedMap4[27] = 't';
// Push back the unordered map in the vector
vect.push_back(unorderedMap4);
print(vect);
return 0;
}
输出
vector :
unordered map : [ 12:e 2:G 21:s 14:k 7:e ]
unordered map : [ 24:v 27:a 13:J 15:a ]
unordered map : [ 53:o 43:o 41:t 19:h 33:P 37:y ]
unordered map : [ 27:t 23:f 16:i 15:s 53:w ]