unordered_map.cend()

// CPP program to illustrate
// unordered_map cend()
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
  
    unordered_map<int, int> ump;
  
    //向unordered_map插入数据
    ump[1] = 2;
    ump[3] = 4;
    ump[5] = 6;
  
    //这里不能修改'it'
    for (auto it = ump.cbegin(); it != ump.cend(); ++it)
        cout << it->first << " " << it->second << endl;
    return 0;
}

5 6
1 2
3 4

unordered_map.cend ( size n )

// CPP program to illustrate
// unordered_map cend()
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
  
    unordered_map<int, int> ump;
  
    //向unordered_map插入数据
    ump[1] = 2;
    ump[3] = 4;
    ump[5] = 6;
  
    cout << "unordered_map的bucket包含 \n";
    for (int i = 0; i < ump.bucket_count(); i++) {
        cout << "Bucket " << i << " 包含 ";
        for (auto it = ump.cbegin(i); it != ump.cend(i); ++it)
            cout << it->first << " " << it->second;
        cout << endl;
    }
  
    return 0;
}

unordered_map的bucket包含 
Bucket 0 包含 
Bucket 1 包含 1 2
Bucket 2 包含 
Bucket 3 包含 3 4
Bucket 4 包含 
Bucket 5 包含 5 6
Bucket 6 包含

// CPP program to illustrate
// unordered_map cend()
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
  
    unordered_map<int, int> ump;
  
    //向unordered_map插入数据
    ump[1] = 2;
    ump[3] = 4;
    ump[5] = 6;
  
    //这里不能修改'it'
    for (auto it = ump.cbegin(); it != ump.cend(); ++it)
        it->second = 10;  // 编译器错误
    return 0;
}  

编译错误：程序中的CPP代码：在函数'int main()'中：
程序.cpp:19:20: 错误：在只读对象中分配成员'std::pair::second'
         it->second = 10;  // COMPILER ERROR